1.Ren and Stimpy, Doug, and Rugrats all premiered on the same day in 1991, and were Nickelodeon's very first cartoons.
2.The Simpsons creator Matt Groening called The Ren and Stimpy Show the "funniest cartoon on TV" and "the only good cartoon" other than The Simpsons.
3.Arlene Klasky, creator of Rugrats, got the idea for the show when on maternity leave. She was inspired by two questions: "what would babies say if they could talk?", and "why do they do the weird things they do?".
4.The original design for Tommy – seen in the first episode – included a red shirt, and not his signature blue.
5.The babies on Rugrats were all voiced by women – and Elizabeth Daily, who voiced Tommy, once recorded a session while she was in labour.
6.Christine Cavanaugh voiced both Chuckie on Rugrats and Oblina on Aaahh!!! Real Monsters – as well as Dexter on Dexter's Laboratory and Babe from Babe.
7.The character designs in Aaahh!!! Real Monsters were partially inspired by The Beatles' Yellow Submarine.
8.The Aaahh!!! Real Monsters trio appeared in a crossover episode of Rugratsin Season 6 of the latter show.
9.The character Doug from Doug was originally called Brian, but show creator Jim Jinkins changed it because it sounded "too fancy" and he wanted the character to have an ordinary name.
10.Jinkins based Doug partially on himself, while Patti was inspired by his childhood crush, Skeeter was based on his childhood best friend, and Roger was inspired by a boy who bullied Jinkins.
11.Doug and Skeeter have such thin hair purely because it was easier to draw them that way.
12.Rocko from Rocko's Modern Life was originally yellow, but the creators were forced to change him to beige when Nickelodeon wanted to get a toy company on board who already had a yellow toy line.
13.Although Rocko's Modern Lifegot away with a lot, the infamous scene where Heffer gets "milked" was cut before being broadcast in the United States, but it was included in international versions of the show and also on the VHS.
14.Hillwood, where Hey Arnold! is set, is a fictional city based on several northern cities in the US, including Seattle, Portland, and Brooklyn.
15.The character Arnold is partly based on series creator Craig Bartlett, who incidentally is married to Matt Groening's sister Lisa. Lisa is the person who came up with the idea that Helga has a crush on Arnold.
16.Arnold's TV debut was actually on Pee-Wee's Playhouse, which Bartlett worked on at the time, as a claymation character in a series of shorts.
17.The creator of Spongebob Squarepants, Stephen Hillenburg, was a marine science educator as well as an animator, and got the idea for the show after noticing how fascinated the kids he taught were by tide pools.
18.Finally, Spongebob was originally going to be called Spongeboy, and the show was named Spongeboy Ahoy – but the name had to be changed when the creators discovered a mop company had already trademarked it.