1 Mark Hamill was the first to voice Zim in the original pilot. Billy West later voiced over his work. Both actors were rejected because their voices were "too well known."
2 Had the show continued, it would have been revealed that Dib, and maybe Gaz as well, were not actually Professor Membrane's birth children, but had been genetically engineered by the Professor, perhaps as an experiment.
3 After Gir drinks something, he often launches into a random coughing fit. What you hear are real-life, recorded coughing fits of Gir's voice actor, who could not perform Gir's enthusiastic slurping noises without aggravating his asthma.
4 Dib is mexican.
5 Gaz's full name is 'Gazlene' (a play on 'gasoline').
Interesting facts, Jessica. Nice list. - ModernSpongeBobSucks
Because she has a 'flammable' personality. Ha. Ha.
6 There are only 30 official invaders.
And we all know Zim isn't one of them, lol
7 Rikki Simons, the voice of Gir, was also a colorist on the show.
8 Dib is Jhonen Vasquez's favorite character.
It's because they belive in the paranormal ( I don't know any more reasons).-Vestalis
I think it may also be because he puts himself into the character. Or that he relates to him.
9 Jhonen has stated that Irkens write in all caps "because they are annoying."
Lol, gotta love his sense of humor.
10 An Irken's PAK filters their blood, contains all their memories and knowledge, and their personality. The PAK "is" the Irken, with their bodies functioning as a host.
Scary.. - TwilightKitsune
11 Rikki Simons, Jhonen Vasquez, and Steve Ressel (the producer) have cartoon cameos in some of the episodes.
Like in "The Wettening".-Vestalis
12 Zim is ambidextrous.
13 Jhonen voices several characters on the show. Namely, Nick, Carl, and Old Kid.
14 Backseat Drivers from Beyond the Stars is Jhonen's favorite episode.
15 The episode Dark Harvest was cited during the Scott Dyleski murder trial.
16 Gaz, Taster of Pork is, by far, Steve Ressel's least favorite episode.
17 Irken blood is clearish pink in color.