Author's Saving Throw: Jhonen Vasquez admitted that, as misanthropic as the show already was, Dib's abusive sister and neglectful father were too cruel to find funny, and when creating the comics, rewrote Gaz from a Flat Character to a more dynamic Annoying Younger Sibling (notably in Issue 14) and had Prof. Membrane interacting with his children a little more. This extended into Invader Zim: Enter the Florpus, which firmly shows that the Membranes love each other in spite of their dysfunction. All to make the cruelty funnier, of course.
Executive Meddling: For the comics, Nickelodeon handed over the rights to all the series' characters except, for some reason, Skoodge, meaning he wouldn't show up until the final issue, albeit just as a single-shot cameo. Considering the tone of the interview, this may have been a joke.
Foodio 3000, a character that debuted in the Oni Press comics, was supposed to debut in the series proper before it was cancelled.
A handful of unproduced episodes from the show's second season were retooled into issues of the comic, these being issues #8, #18, and #50.
Sequel Gap: The first issue released in July 2015, thirteen years after the series ended production and nine years after the last episodes were finally aired on Nicktoons.
The series was usually released on a monthly basis, but occasionally an issue would be pushed back a month or two for a variety of reasons. For example, the monthly ongoing was meant to end December 2019, but delays with the final two issues of the "Battle Void" arc led to the final issue releasing March 2020.
Meanwhile, the Quarterly series was meant to begin the following month, but got delayed to June thanks to the COVID-19 Pandemic.
Word of Gay: In his book Zim Scripts Vol 1: Pigs and Waffles, Eric Trueheart reveals that Groyna from Issue 8 (and the unfinished episode "Pants!") is indeed a lesbian and is in love with her best friend Sheather.
to debut in the series proper before it was cancelled.