Adventure Time/Continuity Nod

For a show that is mainly episodic and is primarily formatted so that it can be watched in any order, it surprisingly has very good continuity. Almost to the point of being a full-blown story arc: "Jake:"
 * The teleportation spell "Razzamafoo" is used in two different episodes by two different magic-users.
 * In the Magic Man episode, Finn pulls out his autotune singing voice that he acquired by swallowing a computer right before "The Jiggler". Jake mentions that he "can never take [Finn] seriously when [he's] singing."
 * In "Evicted!", Finn throws the Enchiridion at a worm.
 * In "Crystals Have Power", . Also, Jake talks about being hopped up on magical power - which happened to him in the previous episode.
 * Because Finn lost his sword in the black hole in "The Real You", he got a new sword with a wooden hilt (which he obtained from the train in "Mystery Train").
 * Finn and Jake pass their gauntlet dock from "Business Time" while pursuing the Lich in "Mortal Folly". Billy's defeat of the Lich (mentioned in "Billy's Song") is also stated as the reason the Lich was imprisoned in amber: Billy pummeled him into it.
 * The "other secret room" that Finn, Jake, and Princess Bubblegum go to to discuss plans to defeat the Lich is the secret room from the beginning of "The Enchiridion!". PB was probably even holding the very same orb.
 * In "Henchman", Marceline returns. Also, the Duke of Nuts refers to his infant son as "my second son." This is as opposed to his first son, the Marquis of Nuts, who is seen in "The Duke".
 * Lady Rainicorn's parents in "Her Parents" use the same kind of translator devices that Lady herself uses in "My Two Favorite People". Theirs seem to have better settings though.
 * "It Came From The Nightosphere" features Marceline's song "Daddy, Why Did You Eat My Fries?", which the Ice King does a hilarious rendition of in "Holly Jolly Secrets".
 * In the former episode, Lumpy Space Princess calls "Drama Bomb" when things take a dramatic, emotional turn. Jake later does the same in the latter.
 * Also in the former episode, the Marauders from "Memories of Boom-boom Mountain" are seen again.
 * In the pilot, Finn says he is twelve. In "Mystery Train" he turns thirteen. Later, in "Mortal Recoil", he says "Thirteen years old? That's how old I am."
 * "Heat Signature" shows that Lumpy Space Princess still lives in the woods, as first seen in "To Cut a Woman's Hair".
 * In season three,
 * In "Memory of a Memory",
 * "Too Young" shows that
 * "The Monster" is a continuation from
 * Also, "The Monster" makes a nod to "Go With Me," when LSP
 * Because of Ice King's in the season two finale, he tries his hardest in season three to be a good friend to Finn and Jake, as shown in "Hitman" and "Still".
 * That wad of Princess Bubblegum's hair in "What Was Missing" is most likely the wad of hair from "To Cut a Woman's Hair".
 * In "The Creeps", Jake makes a few nods to "Mystery Train".
 * In "The Creeps", Jake makes a few nods to "Mystery Train".

"Jake: She's a Finn:"
 * Lumpy Space Princess references "Trouble in Lumpy Space" by mentioning Brad and their break-up.
 * In "From Bad To Worse", Finn and Princess Bubblegum state that this is the second time a Zombie Apocalypse has happened in the Candy Kingdom, making a nod to "Slumber Party Panic".
 * In "Beautopia",


 * In "Mortal Folly", Finn's Hair of Gold is shown to have grown back after he shaved it all off for the tree sprite earlier that season. Later, in season 3 episodes "Beautopia" and "No One Can Hear You", we see that it's grown out some more and is now chin length.
 * In "Thank You", Finn wears the sweater that Princess Bubblegum made for him in "Mortal Folly".
 * In "No One Can Hear You", Finn asks if everybody's at church worshipping Glob, explaining Lumpy Space Princess's "Oh my Glob!"
 * "The New Frontier" explains that Glob is the final judge of a person's sins in the afterlife.
 * In "Wizard Battle", we see Bufo and several of his apprentices, each with a varying number of stars on their robes.
 * There's also the Forest Wizard from "My Two Favorite People" and "Storytelling".
 * In "Marceline's Closet", Finn alludes to "What Was Missing" by questioning the idea of jamming with Marceline without the inclusion of Princess Bubblegum and Beemo.
 * Marceline also says she hides in Finn and Jake's house all the time, which matches her entrance in "Go With Me".
 * In "Another Way", the Enchiridion returns again.
 * Slowly but surely, Finn's hair is growing back; it's now almost shoulder length.
 * In "Incendium", the wad of Princess Bubblegum's hair from "To Cut a Woman's Hair" and "What Was Missing" returns yet again.
 * The season four episode "Hot to the Touch" can easily be titled "Incendium Part II". Also,
 * In "Dream of Love" it is revealed that Tree Trunks and the Pig from "Apple Thief" are now dating.
 * The Nightosphere two-parter ("Return to the Nightosphere" and "Daddy's Little Monster") is obviously a sequel to "It Came from the Nightosphere". Finn remembered the latin chant and used it to get back to the Nightosphere.
 * In "In Your Footsteps", the Enchiridion returns yet again.
 * Jake mentions that PB is Finn's ex-girlfriend, but Finn denies this, saying they never truly went steady.
 * "Princess Monster Wife" briefly shows Günter's offspring which has not been seen since "The Chamber of Frozen Blades".
 * Princess Bubblegum created Goliad because of the events of "Mortal Folly" and "Mortal Recoil".