After playing "The Penal Zone", I'd decided to play the rest of Sam & Max seasons when I noticed something.
Aside from Sam & Max, the C.O.P.S are like one of the fewer characters that have seen in ALL Sam & Max Seasons!
Sybil: In Seasons 1 & 2, "disappears" on her honeymoon with Lincoln.
Bosco: Also in Seasons 1 & 2, also "disappears" to Vegas with Bluster Blaster.
Stinky: Only in Seasons 2 & 3
Grandpa Stinky: Only in Seasons 2 & 3
Superball: An actual character who's been in all three Seasons
Momma Bosco: Only in Season 2 & 3
Jimmy Two-Teeth: In Seasons 1 & 2, "disappears" around Max's reelection.
But, of course, the rest of Season 3 has yet to come and maybe some the other characters might come back.