Horrible Painful Overload Day
Horrible Painful Overload Day was the title that the Irken control brains gave the day Zim was hatched. After being hatched each Smeet is moved into a download chair where the sum of Irken knowledge is downloaded into them - after the sum of Irken knowledge was downloaded into Zim he proclaimed that it was full of errors and boring. He wanted to complain so vociferously enough in fact that he shoved the next Smeet in line back into the chute causing a clog. The clog caused a series of explosions...which ended up blacking out Irk for 5 years.
We would have seen this had the series been allowed to continue - this sequence was to appear in the unmade episode The Trial.