Pajama-Clad Hero

Not bad for a man in his jim-jams. Very Arthur Dent. Now there's a nice man.

—Tenth Doctor, The Christmas Invasion

If there's one thing worse than the advancing hordes of evil turning up on your doorstep and forcing you onto a long quest to save the world, it's when it happens before you've even had your coffee. You finally got a chance to catch some sleep, and got rudely awoken by The Call in the middle of the night, telling you to rush out of the house without so much as a chance to get dressed.

Some heroes spend virtually their entire adventure wearing nothing but their jimmy-jams. On the plus side, they're comfy and warm, and a stylish dressing-gown can lend a touch of the Badass Longcoat. But you do tend to look a tad ridiculous, and a dressing-gown over a long nightshirt may be confused with Sword and Sandal wear, the Middle Eastern traditional costume descended from it, or wizard robes.

Examples of Pajama-Clad Hero include:

Always pajama-clad

Anime and Manga

Technically, Near from Death Note is always in pajamas.
Averted in Peter Pan no Bouken. The Darling siblings are almost always depicted as this, but in this particular adaptation they manage to get their normal clothes before being whisked away by Peter.

Literature

As mentioned above, the Darling children in Peter Pan. Possibly the Trope Codifiers.
Arthur Dent, who hitchhikes the galaxy in his pajamas and bathrobe.
- He finally gets a change of clothes in So Long And Thanks For All The Fish. In the radio series and first two books, Douglas Adams wasn't entirely clear what Arthur was wearing; he wrote a scene for the TV series in which the Heart of Gold provides him with new clothes, but this was vetoed by the director, on the grounds that it was funnier for him to be in his pajamas. Since Adams then wrote Arthur as still in his (increasingly tattered) dressing gown in Life The Universe And Everything, he presumably agreed.
The eponymous character of Jodi Lynn Anderson's May Bird series spends the entire 3rd book in pajamas and a bathing suit.
Georgina in The Magic Light by Gabrielle Alioth. She is transferred onto a magic island from her bedroom, pajama-clad and barefoot. At some point she lampshades this by saying that if she knew she would go on an adventure, she would be dressed more appropriately.
Bilbo from The Hobbit by J.R.R. Tolkien. He also forgets handkerchief and money in addition to starting his adventure in his dressing-gown. Subverted when Dwalin lets Bilbo use his hood and cloak.

Film

Mirror Mask - Helena spends well over half her adventure in her pajamas and bunny slippers.
The kids in The Polar Express.

Newspaper Comics

Little Nemo
Mickey "The Yellow Kid" Dugan at first wore a blue nightgown handed down from an older sister until he switched to his trademark yellow nightshirt.

Puppet Shows

The Pajanimals

Theater

Clara/Marie from The Nutcracker spends most of the show in her nightie, since the whole thing is a dream sequence.

Video Games

Pajama Sam, the eponymous hero of the children's adventure game series, is never seen outside his footie pajamas. (The premise of the game is that Sam deals with things that frighten him after he goes to bed, so his "Pajama Sam" superhero persona makes sense.)
The male or female protagonist in the Playstation game Forty Winks.
Patchoulli Knowledge from Touhou. Even when she's out solving incidents in the fighting games, she's still wearing her pajamas. ZUN says that "It's like how foreigners sleep in their jeans, and go shopping with them too".
You in Fable 3, if you decide saving the world should be done in your sleeping clothes.
Rosalina's dress actually resembles a nightgown, which appropriately fits the fact that she lives far out in space, where it is constantly night out (unless if she is orbiting a Sun).
Vincent from Catherine spends most of the action sequences wearing polka-dot boxers. Not that the ladies are complaining.

Western Animation

In The Film of the Book, Coraline Jones wears pajamas for maybe over half the film.
Alvin, Simon, and Theodore of Alvin and The Chipmunks wear what are essentially color-coded nightshirts most of the time. They change into different pajama separates for bed.
Boo from Monsters, Inc. appears to be wearing a pink nightshirt, lavender stockings, and white socks throught the entire film (except when she is wearing a makeshift costume Sulley and Mike made to hide her identity).
Edmund from Rock-a-Doodle, but only when he's a live-action human. He wears doll clothes after being turned into a cartoon cat by the evil owl.
The Professor from Futurama is always in his pajamas. However, this includes a lab coat, so maybe it's better to say he sleeps fully dressed.
The six-year-old heroes of the series PJ Masks turn their pajamas into their Superhero uniforms for nighttime battles against evil.

Real Life

Hugh Hefner made most of his public appearances in his iconic pajamas and a smoking jacket.

Pajama-clad for one adventure, but usually dressed otherwise

Anime and Manga

Negi Springfield of Mahou Sensei Negima spent the entirety of the Library Island arc in his jammies.
After she recovered from having seen what makes the Simoun tick in Simoun, we see Dominura waltzing about the ship in a slinky nightgown for an episode or two. Bonus points for also having bed-head.
Etsuko from Domu: A Child's Dream spends the last half of the manga in her pajamas, being bed-ridden in the hospital after trauma. She also has the superpowered psychic fight of her life wearing them.
Cardcaptor Sakura: Sakura was in her pajamas when she caught her first card, the Fly. In subsequent episodes, her friend Tomoyo provides costumes.
In episode 52 of Sonic X, Tails gets woken up in the middle of the night by Eggman. He hops in the Tornado in his pajamas, though they're only there for a scene or two.
- Which is odd, because he usually doesn't wear clothes of any kind, not counting shoes and gloves.

Comic Books

The Hulk, believe it not was this, complete with bunny slippers while strapped to the brim with ammo and a BFG, no less.

Literature

Chrestomanci frequently appears in one fabulous dressing gown or another.
A Christmas Carol - Scrooge spends the bulk of the story in his nightclothes - but then he is asleep and dreaming at the time.
In Altraterra series by Yvonne Pioch, Anne spends the first quarter of the book (the ride to Academy) only in her nightshirt as she had to flee with others in haste. Given that she has to ride in it for days without change or a chance to wash it, it created a huge discomfort to her, especially when she arrived to the academy. Imagine being led before the ruling body (which resides in academy) wearing nothing but a ragged, partially ripped, smelly nightshirt...

Live-Action TV

The Tenth Doctor spends a good deal of time running around in his jim-jams after regenerating, even engaging in a swordfight before changing into his dayclothes.
- He even made a remark about Arthur Dent toward the end, suggesting that the two may have crossed paths once (Which, considering that Douglass Adams used to be one of the writers for Doctor Who - Life, the Universe, and Everything started out life as a rejected Doctor Who script, is possible).
- Also, Amy Pond in "The Beast Below".
Omar Little from The Wire goes for a walk to get Cheerios in his turquoise pyjamas. Everyone who sees him flees.
Carl Montclaire wears pajamas in All Lizards Go To Heaven, Part 2.

Video Games

In the Commander Keen game Keen Dreams, Keen goes through the entire adventure in pajamas and pink bunny slippers.
Ness wears pajamas during his trip to Magicant.
- In America. In the Japanese release, when Ness woke up in Magicant, he was in the buff and stayed that way save for his Nice Hat.
At the beginning of The Legend of Zelda the Wind Waker, Link starts out in his crayfish pajamas, until his grandmother gives him his signature hat. In a New Game+, the clothes are invisible, as only the honest can see them. Thus, he has nothing but his pjs to go adventuring in.
In Oogie's Revenge, the easiest unlockable costume for Jack to get is Pajama Jack (and bonus: they're different and more colorful than the plain off-white ones from the movie, and they've even got little Jack 'O Lantern slippers).
Naruto from Naruto Ultimate Ninja Storm has a downloadable costume where he can fight in his pajamas. Save his special/Ougi, all his animations are intact, including tightening his headband that's not even there.
Johnny Dash, the hero of the PC side-scrolling platform game Monster Bash, published by Apogee.

Web Original

The Whateley Universe's Negligee Nightingales.
Homestuck: You add a SMUPPET to the mix to make a softer and more stylish RED PLUSH PUPPET TUX. It is like walking around in snugly pajamas. ACTION PAJAMAS.
- Given that dream self clothing is effectively pyjamas, this is now Rose and Dave's default attire following being revived as their dream selves after death.
- Karkat also describes anyone who has reached God-tier as wearing pajamas, particularly John

Western Animation

In the episode "The Good, The Bad, and The Eggly" of the Veggie Tales spinoff series, The Cartoon Adventures of LarryBoy, LarryBoy and Dark Crow end up wearing footie pajamas and paper bags as costumes after their real ones get turned into over-easy eggs.
It happened once to Kurt and Kitty in X-Men: Evolution.