It's a Mad, Mad, Mad, Mad Marge

The way Otto is dressed at his wedding, and other visual elements recalls November Rain, a marriage-themed heavy metal video by Guns n' Roses.

It is very likely that Otto would be fired over his proposal. He took a bus full of students on an unauthorized field trip to make his proposal to Becky, and parents would likely complain about students arriving home late. No consequence of Otto's actions is seen, and Otto's boss (Principal Skinner) was even at his wedding though it is likely he was forced to invite him to avoid being fired.

References Mieletön, mieletön maailma (1963)