Archie had a neighbor that moved and then was a detective in the precinct. Same character. The Puerto Rican neighbor.

It has been a long time, but that's how it was told when I was watching it 1st run.

Edit: I may be remembering backwards. He may have left the precinct and moved into Archie's neighborhood.. ..

2nd edit: same actor, different character. No clue where I came up with that wraparound story, but I was solidly convinced it came from the show.