Speech Bubbles

Comics

 * Most comics use different forms of speech bubble to represent telepathy, internal dialogue, phone calls etc., etc.
 * The Invisibles uses this to good effect.
 * And don't forget the distinctive yellow bubbles and boxes utilized by Deadpool. He certainly can't.
 * This has been in the Doctor Who Magazine comic strip a few times. Most notably, the distinctive voice-treatment given to Daleks is represented as an angular font in a jagged speech bubble. This has been the case since they had their own strip in TV Century 21 in the 1960s.
 * Several characters in The Sandman have distinctive speech bubbles or fonts—each of the Endless and Matthew, in particular. At one point, Matthew "imitates" Morpheus with a speech bubble that looks like his. Delirium's speech bubbles contain wild swirls of color and wavering text, but when she was Delight (and sane), the colors were subdued and straight, and the text linear.
 * Death is the sanest and most down-to-earth of the Endless and the only one whose Speech Bubbles are completely normal.
 * Jamie Madrox's duplicates in X-Factor get slightly different fonts from standard speech bubbles.
 * In Asterix, the language of the Goths is represented by a Gothic font, Greeks speak in an angular font resembling the Greek alphabet, and Egyptian speech bubbles contain hieroglyph-style rebuses (even for onomatopoeia). When Obelix repeats a phrase in Egyptian, it looks like a shakily-drawn stick figure.
 * Asterix and the Cauldron featured a Roman tax gatherer whose rectangular speech bubbles resembles modern tax forms, complete with check boxes.
 * In Asterix and the Roman Agent, anyone falling under the discord-sowing powers of Convulvus (the titular agent) gets a speech bubble tinted green.
 * When our heroes complain to the camp cook about the army food in Asterix the Legionary, the cook responds with mocking sweetness, before yelling his head off. While he's being nice, his speech bubbles are filled with smiling suns, flowers, singing birds and music notes.
 * Nearly every important character in Watchmen has either a different color/style speech bubble, or a different font. Sometimes both.
 * Of The Avengers, the Vision traditionally spoke with a square bubble to indicate a cold, robotic voice, and in the late 90s, Thor was given a distinctive font inspired by Olde English to match his Shakespearean/Biblical patois. More recently, Iron Man has been given red outlined bubbles to indicate that his armour alters his voice.
 * Ultron has been given rectangular shaped bubbles a lot in more modern times, and Jacosta, one of his creations and a manstay of the current Mighty Avengers lineup, speaks with a font that seems like Comic Sans/Arial as opposed to normal lettering.
 * Deathurge speaks with all black Speech Bubbles as does Doorman after he takes up Deathurge's mantle.
 * Super-Skrull speaks with green Speech Bubbles in Annihilation: Super-Skrull.
 * Speaking of Annihilation, in the Drax The Destroyer tie in all aliens speaking in their native tongues get weird bubbles plus in the series proper Annihilus gets purple ones, Tenebrous gets black ones, Aegis gets red ones, and The Xandarian Worldmind gets square ones with a yellow border.
 * The Preservers in Elf Quest originally spoke with wavy lettering, and when the series collected for the first color edition each preserver spoke with its own color of bubble. This was dropped in the Marvel reprint which was completely re-lettered, and the new lettering carried over into some collected editions. The DC Collector's Edition and Online Edition of the Original Series use new computer lettering, restoring the wavy Preserver style and colored bubbles.
 * Elf Quest also used to represent telepathy (sending) by parallelogram-shaped speech bubbles with sawtooth edges. This apparently just became too much hard work, and was eventually replaced by bubbles comprising two concentric ovals, although as you've seen from the above examples some of the original versions survive in the online edition..
 * In PS238, aspiring supervillain and world conqueror Zodon has a chip inserted into his head to make him stop cussing all the time. The innocuous words that replace his attempts to swear are rendered in a blocky font.
 * When he really goes ape-, he starts singing show tunes.
 * Nick Zerhakker in Skin Horse has a similar problem. He doesn't sing, though. Yet.
 * Depending on the writer, various Marvel Universe characters have distinctive font and speech bubble styles, including Ben Grimm (pretty much all the time) and Johnny Storm (whose speech bubbles take on a fiery appearance when he's using his powers); and Wolverine, particularly when berserk.
 * In Don Rosa's early The Pertwillaby Papers series, nearly every character had their own specific font and speech bubble design, reflecting their personalities. The tradition carried over to his Scrooge McDuck stories in part later on.
 * In Atomic Robo the titular character's speech bubbles are blue with small zig-zags on both sides and have a lightning bolt shaped tail. Helsingard as a Brain In a Jar has brown square bubbles. Everyone has a jagged outline over a radio and a dotted one when they're whispering.
 * The various Transformers series use different bubbles for the Transformers. Originally, they were pretty basic bubbles, with the edges of the arrow leading up to the bubble resembling a stylized jagged lightning bolt, like had been often used with television and radio dialogue. Later issues game them a squared bubble. Unicron got bubbles edged in rippled darkness and blood-red lines. Later series added more effects, often to differentiate not only individual characters but their state. (Dream Wave Volume 3 Megatron, for example, had black speech bubbles with white dialogue.)
 * In Teri Sue Wood's Wandering Star, all the characters have elaborately hand-drawn dialogue, except for a group of mind-controlled slaves; theirs is typewritten.
 * Buck Godot: Zap Gun for Hire uses different bubble styles and fonts for different alien races. This page alone has thirteen different bubbles.
 * Normal humans as well as the titular character of Hellboy have white speech bubbles with standard comic book font and short trails. Demons and horrors generally have red or purple speech bubles with longer, wavy trails and sharp letters. Aquatic creatures have blue speech bubbles. The demon Ualac goes from normal white bubbles to wavy golden ones when he becomes the beast of the apocalypse.
 * Disney had for a time comics about baby versions of their characters. Baby Gyro Gearloose spoke in speech bubbles outlined by equations and formulas. Considering Gyro is the inventor as well as being terribly scatterbrained, that it probably represents that his mind's elsewhere while he's talking.
 * In Teenage Mutant Ninja Turtles Adventures when a character is upside down, the text in their speech balloon would be printed upside down as well.
 * This is quite a common gag in many comics.
 * The biochips in Rogue Trooper have sort of semi-circular indentations in the edges of their bubbles.
 * In Atavar, the Uos' speech bubbles are square and all their dialogue is bold. In the first few panels, before Atavar gains the ability to speak their language, the Kalen's dialogue is represented by random Greek letters.
 * In Pogo, P. T. Bridgeport spoke in circus posters, Deacon Mushrat used Olde Englishe lettering, and Sarcophagus MacAbre (the natural-born buzzard) spoke like a sympathy note.
 * The speech bubbles in Cerebus the Aardvark could be incredibly expressive and as artistic as anything else that was going on in the comic, especially when Cerebus was drunk, mad, or having an argument with himself.
 * Null of Halcyon seems to 'speak' through black narration boxes with white text, which doesn't stop anyone from hearing him. The font also changes when characters are speaking in a foreign language, a la Discworld.
 * Manfred Schmidt, author of German comic Nick Knatterton, commented that they were a primitive tool in his POV - "bubbles coming from the heads, eyes, ears, noses or mouths of characters to indicate what they think, see, hear, smell or say".
 * In a number of 2000AD strips, including Judge Dredd and ABC Warriors, Robots speak with baloons that have harsh angled edges rather than curved, occasionally with a different typeface from organic characters (dependent on the letterer).

Manga & Manhwa

 * Many Scanlations groups use this to great effect.
 * Death Note does this, at least in the English manga. The shinigami speak in a different font than the human characters.
 * D.N.Angel uses this trope as well. Dark speaks in a curly fancy kind of font.
 * The Occult Club president from Mahoraba alternated within each word between two different methods of writing Japanese, hiragana and katakana, and the scanlation I read represented this by capitalizing eVeRy OtHeR lEtTeR.
 * Mokona in Tsubasa Reservoir Chronicle (original version) speaks in a rounded font. It takes a while to learn to read it...
 * Kengamine Nagi in Deadman Wonderland speaks with a synthesizer, which is illustrated through squarish, angled speech bubbles (as opposed to the round ones that the rest of the cast gets.
 * Yotsuba in Yotsuba&! speaks entirely in hiragana, the first form of Japanese writing children learn, which emphasizes her age. This effect, alas, has not been reproduced in any English translation.
 * Speaking of Yotsubas, Satsuki Yotsuba in Negima has a unique way of speaking which is portrayed in the manga by her almost never using speech bubbles. Her dialogue is almost entirely in the side scribbles normally used for aside notes by manga characters.
 * Also, the French official translation render's Chachamaru's (and strangely, Kokone's) bubbles with a different font to reflect a robotic voice.
 * Berial in The Tarot Caf Ã© speaks in an elegant Gothic font.
 * Fruits Basket uses odd-shaped panels and unusual fonts throughout to convey emotions.
 * At one point in Sekirei, Kazehana greets Minato upon his returning home and her dialogue appears in heart-shaped speech bubbles... at which point Miya scolds her about this, claiming they're against the rules.
 * Ai Yori Aoshi and other manga with romance in the plot often have bubbly speech bubbles to represent nervous babbling. Sometimes the bubbles will have their own Sweat Drop.

Literature

 * In what will probably be the only example of characters in prose literature speaking in dialogue balloons, Who Censored Roger Rabbit? (Literature)? by Gary K. Wolf features a world where human beings live side-by-side with cartoon and comics characters. The 'toons communicate via visible dialogue balloons (they even come out of the phone), but can learn to enunciate verbally if they so desire.

Manhwa

 * Priest uses this a lot; Protagonist Ivan, spirit guide Belial, big bad Temozerala, his demon lieutenants when they transform, and the zombies all have their own fonts.

Music

 * The Bonzo Dog Doo Dah band used speech bubbles in live performances for comic effect, saying things like "Wow! I'm really expressing myself!"

Video Games

 * In SaGa Frontier, the words in your character's speech bubbles are different colors than everyone else's. If you run into another one of the main characters during a storyline, their words are the same color as your own.
 * City of Heroes represents characters' speech in speech bubbles. Players can choose the color of their bubbles and text.
 * In Star Control 2, each race's speech is subtitled in a different font. These vaguely match their personalities, so the Ur-Quan have large, bold text while the Utwig have thin, wobbly, depressed-looking text.
 * The Paper Mario series love to play with the speech bubbles. Characters talking normally have a regular rounded bubble with normal font size. If a character is extremely shocked or angry, not only the font goes all caps, but the font size grows HUGE and sometimes the speech bubble becomes more pointy instead of round. Characters who are scared or angry may use fonts that wiggle and characters who are very quiet or growing quiet have the font shrink and/or become a light gray instead of the standard black. Truly evil characters have a purple speech bubble.
 * In Paper Mario 2 at least, Boss characters also have a different sound effect that goes with the scrolling text in their speech bubbles.
 * The Mario & Luigi trilogy shares this love for playing with the speech bubbles.
 * In Vampire: The Masquerade Bloodlines, the malkavian font is like cut out letters from a paper.
 * Video Game/Banjo-Kazooie and Conkers Bad Fur Day have them throughout each cutscene.
 * In Final Fantasy IX, every character has them throughout the game, even with the scrolling text in them.

Web Comics

 * In A Moment of Peace, humans have normal speech bubbles and gods speak in floating, colored, Comic Sans MS text.
 * In Exterminatus Now, the Dark Gods have different colored speech bubbles and fonts, and the main character's superior's speech bubble is black with white text. He himself is nearly always in shadow. The writer pointed this out in the comments for the comic.
 * Xawu has light pink-ish Boxes with black text for Hori, Black with white text bubbles for the bartender, green for Rikard, Purple for Faren, blue for the Pufkash, pink with no border for the princess, and normal ones for Tyrus and unimportant characters. Most also have their own font.
 * Gunnerkrigg Court uses a different color balloon for each character; the differences are usually subtle. When Shadow2 copies another character's voice, this is indicated by his balloon's color. One character's bodily possession is indicated by overlapping balloons.
 * Initially even minor character got their own bubble colors, but this was later dropped; in later chapters, only the major characters get colored speech bubbles. Most minor characters have even lost the bubble colors they once had (e.g. Paz, whose bubbles used to be brown, but now are a generic white).
 * Similarly, Irregular Webcomic uses different colors for different characters, or at least tries to. Many characters and many crossovers have lead to a few cases where multiple characters in a strip speak with the same (or very similar) colors.
 * Richard from Looking for Group falls under this proposed trope.
 * Order of the Stick uses numerous variations in the shape or color of the Speech Bubbles for specific characters:
 * Undeads uses black speech bubbles with white text. When Xykon becomes a lich in Start of Darkness and his speech bubble changes to the undead format, he comments on his dramatic, echoey voice.
 * Diverse colored speech bubbles for outsiders such as celestials, infernals, and ghosts. Infernals usually have black speech bubbles with colored text inside (lampshaded with Qarr the Imp, who is recognized by his red-on-black speech bubble). Celestials have brightly colored bubbles with black texts. Elementals like Celia have a color related to their plane of origin.
 * Dragons and half-dragons also have colored speech bubbles related to their species.
 * The shape is sometimes significant too, like with modrons having rectangular bubbles.
 * The arrows pointing to which character is speaking also give indications. They are straight when the character is healthy, but become irregular for a wounded or dying one to represent shaky speech. Minister Malack's are always this way, hinting of a raspy voice.
 * anti-HEROES does the same as Order of the Stick, and lampshades it.
 * Erfworld uses one font (Maiandra GD) for real-world characters (including Parson even after he is summoned into Erfworld), and another (Gorilla Milkshake) for Erfworld's native inhabitants.
 * Coga Suro has the usual convention of robots having square speech balloons. Most of them, anyway. Styx, an evil example, has black speech balloons with white text. For a few chapters, each character had a different font, but this was dropped later.
 * Chainmail Bikini uses a different font for each player (with the same font being used for table talk by the player and in-character statements by that player's character).
 * The Wotch uses a black speech-bubble with white letters for Dark Lord Xaos. During a flashback, you see the moment where he discards his old persona as the Lawful Good "Worlock", and dons the spikey darkey helmet of Lawful Evil Lord Xaos; his speech-bubbles reverse their colors from one panel to the next.
 * 8-Bit Theater has the Dark Warriors, were everyone but Bikke has weird speech bubbles; Garland's are red on black (formerly black on gray), Drizz'l's are white on black, and Viblert's are black on red. There's also Sulk's (a whiny version of The Hulk), which are green. The Light Warriors also get uniquely-coloured text when they don't speak in normal speech bubbles; this has led to much discussion over the identities of the speakers in one particular comic.
 * A question which has recently been answered. (Spoilers!)
 * Bob and George has the Shadowy Author, whose bubbles are normal colored, but just float around without the tail pointing to his mouth. About two years before the end of the comic, his speech balloons suddenly gain a tail;.
 * Dream Catcher typically uses a standard font for everyone, except early on in the gateworld where they briefly used hard to read cursive text.
 * Agatha and other "Sparks" in Girl Genius get a gradual change of font as they draw more and more on the madness that is their source of power... it's not just for decoration, either. With all the cool machines the Sparks can build, it's easy to forget their most insidious power—the ability to draw the easily-impressionable to them, binding their wills, and turning them into "minions". When the font starts getting curly, people start kneeling. Agatha just has a bit of extra punch in that department, thanks to her  blood.
 * When Bangladesh DuPree breaks her jaw and has it wired shut, her speech bubbles become rebuses.
 * Other groups that have their own special speech bubbles: Jagerkin (and the Generals are even more special), and and voice-enabled clanks. Castle Heterodyne has a bubble similar to the Jagers, and Von Pinn and the Geisterdamen have their own particular fonts, but the same speech bubbles as human characters.
 * Actually, Von Pinn has her own very distinctive bubbles, with curved slices all around the edge, faintly reminiscent of a circular saw blade.
 * Metroid: Third Derivative gives every character a different font, color, and text effects for their speech. When JD copies Joey's voice in comic 160, his color changes to indicate it.
 * Mr. Square has often used word bubbles as actual characters in comic 12 and 143 as well as using them as scenery in #48.
 * The Last Days of Foxhound does the inverse. When Decoy Octopus is in disguise, his speech bubble remains white, making it easier for readers to identify him.
 * Each character has their own colors of speech bubble, with their own Painting the Medium moments. When Psycho Mantis is using his powers, his text turns from black to red green. It's when he goes totally nuts that his text turns red. And when one character is possessing another, the possessing spirit's speech bubble is used. This is actually used in the last comic, to reveal that.
 * In Ozy and Millie, all the dragons have their own distinctive fonts.
 * Lampshaded in the April 10, 2006 strip.
 * Vinci of Vinci & Arty has a thick Greek accent, which is generally rendered phonetically only when other artists "borrow" him. In his home comic, it's represented by a pseudo-Greek font.
 * Most characters in Vinci & Arty have distinct fonts, with the exception of non-recurring characters, who just get a generic font.
 * Combo Rangers (hey, there's no such thing as notability, right?) has speech bubbles Color Coded for Your Convenience, in accordance to the character's uniform colors. This was useful when it was revealed that a Big Bad was a clone of Power Combo, thanks to their similar speech bubbles.
 * Since the characters of 1/0 are actually in a comic strip, they have no audio even to them; their voices are distinguished instead by their fonts.
 * Well, they seem to "hear" their voices, but in the same sense that we do—by seeing the fonts and imagining how they sound. This provokes a bizarre conversation halfway through the strip where they begin arguing about what their voices sound like. Zadok the grass golem is told that only he thinks his voice is a sexy rich baritone instead of a creepy rustling scratching.
 * Kim & Jason
 * Kismetropolis uses different speech bubbles, colors and fonts for varying purposes.
 * In DM of the Rings, the GM spoke with square speech bubbles with yellow background, and NPCs (played by the GM) had regularly shaped speech bubbles, but also with yellow background.
 * This convention was picked up by Darths and Droids.
 * And in the recent Deep-Immersion Gaming portions of The Wotch.
 * The B-Side Comics from Apple Geeks use a similar system: conversations between the artist and writer have the artist speak normally through his avatar and the writer using only square speech balloons while remaining offscreen, almost as a Narrator.
 * David Hopkins' Jack uses a very distinctive style of speech bubble for any dialogue spoken by the Sins in the strip and a second distinctive style for those characters who are/were Fallen angels, although the latter is rarely seen.
 * Candy and Ryan Dewalt, the pair behind Vinci & Arty, did a story arc for Jack (with full approval from David Hopkins) and brought their talent for character-specific fonts to Jack.
 * The first panel on page 10 of the Energize/Dasien crossover uses a small drawing of each hero's face next to the relevant speech bubble.
 * Home On The Strange has one character speak in a different font from the others. There's a good reason for this, which is explained in the sidebar.
 * One strip from Lick My Jesus (which is regrettably defunct) had one character agreeing with everything another said. It turned out to be because he didn't understand what the person was saying—because he didn't speak Papyrus. The rest of the strip was a series of gags which involved treating fonts as if they were languages.
 * Most dialog in The Easy Breather is set in three standard Apple fonts: Chicago for heroes, Sand for villains and Chalkboard for other characters. In the second story, the "neutral" dialog font was changed from Chalkboard to Rehotalko, and Self Destruct Button is used for talking robots.
 * In The Inexplicable Adventures of Bob, Starfish Aliens often speak in hexagon-shaped balloons, while robots usually speak in stylized square balloons reminiscent of the Marvel Comics Transformers.
 * In Schlock Mercenary, the Big Bad race of the time had an in-universe font change to something more readable as part of the terms of a surrender.
 * Miss Delta (a digital artist from @hens) in Adventures In ASCII has half-triangular speech bubbles reflecting her body shape.
 * CRFH's speech bubbles are mostly in the distinctive "Good Dog" font, but Satan has his own font, and the cyborgised Brazil speaks in a plainer font to suggest his computer-synthesised monotone.
 * In Kagerou, different colors are used to differentiate characters, as well as to show which of Kano's personalities is at the fore. His speech bubbles usually match his Kaleidoscope Eyes.
 * One special Mountain Time episode puts speech bubbles to a somewhat meta use.
 * Although Something*Positive mostly uses standard speech bubbles and fonts, this strip deserves special mention for its humorously creative use of bubble colour, heavy outlining and symbols such as storm clouds, teardrops and a dead kitten to convey heartbreak.
 * The Way of the Metagamer started out using Comic Sans for everything. Later on, it switched to Gemelli—but when characters are under mind control or otherwise possessed, their font changes back to Comic Sans. Additionally, the narrator speaks with floating rectangles instead of bubbles—whenever a character imitates the narrator, they too use rectangles.
 * Drowtales uses differently colored speech bubbles for different characters. In one panel, Ariel and Chirinide both yell at Kyonne to leave them, and share one bubble with a gradient between their respective colors.
 * El Goonish Shive has mostly normal speech bubbles, but occasionally, an Immortal (or flat out Eldritch Abominations) get black speech bubbles that get progressively less normal as they get angry and/or emotional. The Goo doesn't even have a speech bubble, subtly implying that the Goo does not speak using vocals, but instead through telepathy of some sort.
 * Also, in one strip, where a new character with long hair is introduced, a little bubble naming him shows up with 'gothic' script. He glances over and notices it, physically strikes it with a fist, and it reverts to normal text. It's in the 'one shot' strips, though, where that's more common.
 * Little Worlds features blurry-edged color-coded speech bubbles for each of its characters.
 * Keychain of Creation has the usual (round, black text on white), and a number of special ones:
 * Yelling is indicated with spiky bubbles.
 * Some Abyssals or otherwise death-aspected creatures get white text on a black background.
 * Marena has a more animalistic font when in her Deadly Beastman form.
 * Nova and the have rectangular bubbles, with rounded corners.
 * Unnatural Mental Influence is often indicated by the text having a color.
 * In The Unspeakable Vault of Doom, The Unspeakable's speech bubbles use the Caslon font, as opposed to a "normal" comic font for other characters.
 * Also, when Zalgo comes (and goes) in one of the strips, his speech bubbles are oddly-colored and covered in swirly lines.
 * Kevin and Kell has started altering its bubbles; once converstations start showing up in 'feline', the bubbles grow cat ears and whiskers.
 * Game Destroyers does things a little differently than most other web comics. Unlike other comics, there are no dialogue arrows on the speech bubbles in this comic. Instead, each character has a unique font, text color, and background color. Some characters who know telepathy speak in a rounded edge rectangle instead, whenever the author remembers that, anyway.
 * In Roza, the guard monster roars in red.
 * In Precocious, speech with asterisks.
 * In Dreamkeepers Prelude, an arcing speech bubble.
 * In Thistil Mistil Kistil, Loki is angry. The lettering is not neat, and shows red.
 * In Sinfest, using fonts, and no border for Buddha's awakening
 * Squigley's Mushroom Samba features his "WOW" turning into a bird.
 * In The Specialists Baron Crossbones speaks in black bubbles with white writing.
 * In American Barbarian red, white, and blue speech for a moment.
 * In Blue Yonder, one attacke speaks in white writing on sky blue. All the rest are normal.
 * In My Life at War they use the shape of speech bubbles to indicate a character's accent.
 * In Level 30 Psychiatry translated Pokémon-Speak is rendered in Blue and Yellow balloons reminisant of the Pokemon logo.
 * Naturally, these get used throughout the whole of Ears for Elves; however, the ways their shape and layout can be used is shown excellently here.

Western Animation

 * Many cartoons of the silent era such as Felix the Cat would use Speech Bubbles as opposed to the word cards usually seen in live action silent films.

Real Life

 * Toon Lagoon at Universal Orlando's Islands of Adventure is inspired and populated by the characters of King Features Syndicate, and has dozens of speech bubbles (and indeed, entire cartoon set pieces) deployed throughout the island for making amusing photographs.