These are some references used for drawing Zim in season 1. I love to see all the details and comments made by the artists. Also, you can start to see the differences between pilot style and early season 1 style here. Thank you to Soapy Waffles for bringing these to my attention!
After Invader Zim was cancelled, Nickelodeon still wanted the Christmas special for the last episode. Production ended for the rest of the show, but they finished this one. A couple episodes including Minimoose’s proper introduction to the show were completely skipped, leaving them no choice but to explain the character’s sudden appearance with this scene. An idea that sadly never came to fruition was that immediately after this, there would be a short montage of flashbacks to previous episodes with Minimoose added into various scenes, showing that he was indeed “with him the whole time.”