Basically he’s been in a coma for the past 22 years, and everything has taken place in Homer’s head. Maybe. H/T: Reddit.
And now Redditor Hardtopickaname has put forward a fairly crazy theory about the series.
20th Century Fox / nohomers.net
The theory goes that in October 1992, the episode "Homer The Heretic" first aired, a key scene of which has Homer talking to God.