1. There is a strange theory about the Garfield that states that Garfield is actually the only “real” character. Jon and Odie are simply figments of a starving, lonely, and desperate Garfield's imagination. Need proof? This theory was actually suggested in one of the Halloween specials (partly pictured below).
2. The existence of Spongebob and his strange friends (a talking squirrel, an evil genius plankton, etc) is the result of radiation from nuclear arms testing that was performed on the Bikini Atoll in the late 40's and early 50's. Since the characters live under the atoll, the town is known as 'Bikini Bottom'. - source
3. In Alladin there is a scene where Genie calls Alladin's clothes "so 3rd century". But genie has been in the lamp for over 10 thousand years, so there's no way he could know of the fashion trends which have gone on while he was trapped. Genie also makes reference to contemporary figures such as Groucho Marx and Jack Nicholson.
If Genie really was referring to the 3rd century (AD) and if he actually did spend 10 thousand years in the lamp, then it is AT LEAST the year 10, 300 AD when he gets out and meets Alladin.
Conclusion: The film takes place in the distant future, a post-apocalyptic world where only Arab culture survived. The name "Arabia" changed over time to "Agrabah." Incredible technology from previous civilizations still exist, such as sentient flying carpets, or genetically engineered parrots that can talk and actually understand language. The inhabitants of this distant future simply see all this technology as "magic" however. - source
4. In Pinky and the Brain, it is actually the lovably "stupid" Pinky who is the real "genius” and Brain who is “insane”. (Recall the ambiguous nature of the theme song - One is a genius, the other’s insane... but which one's which?).
Brain constantly plans to take over the world, making him pretty insane by most definitions. He's a megalomaniac, obsessed with power and the subjugation of others. Pinky, on the other hand, often finds ways to ruin Brain's disastrous plans and save the world.. so.. who is the real genius? - source
5. The "Eternal Happiness" Theory of the Pokemon anime states the following: Basically, in episode one of the original show, Ash sees the legendary Ho-oh pokemon, which is later stated in a Pokedex entry to grant eternal happiness to whomever sees it. Ash's eternal happiness is being able to be a kid and explore with his Pokemon forever, which explains why he never ages past ten despite the show going on for years. Screencap of the Ho-oh from episode one:
6. In Rugrats, have you ever wondered why Angelica is the only non-baby character that can talk to and understand the babies? Well according to this popular (but dark) fan theory, Angelica understands them because they are figments of her imagination.
Angelica's parents are mean, inattentive, and distant, which makes her escape into a fantasy where she can vent all her frustrations on non-existent characters. There is even an explanation for each imagined baby:
-Tommy died soon after childbirth, a fact reflected by the fact that his father Stu never leaves the basement, inventing toys that his son will never play with,
-Chuckie died in the car crash along with his Mum, also reflected in the actions of his father; the crash has made him a pathetic nervous wreck most of the time.
-And then there is Phil and Lil. There never were any twins, there was just one baby. However this baby was a still born, and Angelica never knew the sex of the still born, so she invented twins of different genders.
7. There is pretty good evidence that suggests the world of Samurai Jack takes place in a post-apocalyptic version of Townsville (From Powerpuff Girls). There are scenes in Samurai Jack that show broken down billboards that are identical to ones shown in Powerpuff Girls. See below for proof.
8. In Courage the Cowardly Dog, Courage is actually just a normal dog and the audience sees the world through the dog's eyes. All the villains in the show are just normal people, and all the creepy and unexplained occurrences are just normal happenings, but to a dog they seem terrifying. The fact that the family lives in "The middle of Nowhere" just points to the fact that Courage doesn't know anything about the world outside of his immediate surroundings, perhaps because his owners are too old to actually take him out for walks.