The flashbacks show Oscar and Blanche living in the same apartment as the one in which Oscar shares with Felix. The opening narration says that Oscar had been thrown out by his wife. If Oscar had been thrown out of his residence by his wife, it would have meant his moving into a completely different apartment.
During one of the flashback scenes, Felix tells a joke that mentions Monday Night Football in its punch line. The events of the flashback took place sometime in the early to mid Sixties, and Monday Night Football did not debut until 1970.