How long did Dib get to live? How did he die? What did Zim do with the rest of his life besides watching Dib’s children grow? What odd jobs did he take to pass the time? Is he still in touch with Gir?
Whatever happened to Sizz-lor?
Dib lives an abnormally long lifetime because of the human compatible PAK he, Zim and Dipper designed. Not a long life by Irken standards, but a very long one by human standards. His death was brought on by old age, dementia and damage from many decades of smoking cigarettes (he attempted to quit several times, but it never stuck).
His career as a super scientist was successful even if it wasn't his passion. Dib continued to study the paranormal on earth as well as join Zim on several space adventures before his final hour.
Dib was never able to convince his "legitimate/ real science" colleagues that the paranormal and supernatural are legitimate fields of study, but he was respected among the younger generations of paranormal investigators/ enthusiasts.
Dib never opened an official school for paranormal studies, but with Dipper's help/ support they converted the Mystery Shack into a lecture hall on paranormal studies.
As for Zim, he also kept very busy. He never officially joined the resisty, but provided aid whenever he could. He smuggled lots of snacks, weapons/ tech and provisions for the resisty.
He spent a great deal of time and effort illegally downgrading PAKs for Irkens seeking to leave the empire as well as collecting "forbidden" data from set PAKs for future resistance efforts.
He helped construct a power grid for Mem's hive. He helped Gir open a speak easy cantina in Mem's hive as well. He upgraded Mini Moose and gave him to the resisty to build up their defenses. [Mini Moose was cool with this, as he was originally built from Vortian tech.]
Zim explored space for many years, hiding from the gaze of the control brains; stealing ships, tech and weapins. He also sold a great deal of set stolen tech.
He started a band, let the fame go to his head, got kicked out of the band. He enjoyed the company of a rotating list of lovers. He perfected his casserole recipe. Yeah. Zim lived life for sure.
Sizz-Lorr took Gir on as his apprentice and helped him become a Frylord in his own right. Sizz-Lorr has always been very vocal about service drone rights and the importance of stable snacking systems; which put him on this ice with the control brains for decades; part of the reason why Shloogor's is understaffed so often.
Tallest Purple/ the red brain does eventually agree to send Sizz-Lorr more help. When the control brains complete their big upgrade, however, many of the improvements Sizz-Lorr and the other frylords demand are denied. Investigations against him suggest Sizz-Lorr has been low key assisting the resisty and conquered labor forces for decades. Sizz-Lorr is put under strict observation and is eventually accused of conspiring against the empire and is imprisoned.
Gir is devastated by this, radicalizing him even more than he originally was...
So much I'm glossing over here. Wish I had time to go into depth, but this post could potentially be a novel long if I keep rambling.