Second of all, Doctor Doom introduces us all to “The Micro-World,” a very early precursor to the Microverse. They call on Ant-Man for help to deal with Doom’s shrinking technology.
In any event, Thing genuinely falls down a hole. Up to now, he’s busted up through a floor—this falling down a hole is more of what will continue to happen to him. It’s a running gag.
First appearances: None
For the complete history of the MU, year by year, go here.