I can’t remember if it was a tv show or movie but it had a guy who’s wife was super annoying and he had day dreams of killing her. Towards the end he feeds her to monster under a desk at a school I think it was. I coulda swore bill Murray was the guy but my searching has come up with nothing
sounds like “The Crate” from Creepshow (1982)
http://www.imdb.com/title/tt0083767/?ref_=fn_al_tt_1
Agree with GG.
definitely Creepshow.