Larry Lindville, the actor who plays Detective Hugh, is best known as Major Frank Burns from MASH.

This informant, TJ, is a different actor than the guy who played the original TJ in earlier seasons.
If you've seen the Leslie Nielsen comedy "Police Squad!", you will see it featured the exact same character, same actor, same role, a shoe shine informant only his name is "Johnny"
This from Wiki:
"Drebin frequently needs to meet with Johnny, the omniscient shoeshine boy who knows everything, for "the word on the street". Johnny won't actually tell Frank anything until Frank slips him a bribe (often saying, "I dunno anything about it," or, "It's a big city," until he's paid). Each time Frank leaves Johnny, a specialist or celebrity arrives, and asks Johnny for advice about their particular profession"