I would've thought that Looney Rooney was with the show since its inception in 1968, but the Wiki article says he joined the all-lib cast in 1979.
Apparently Looney Rooney's commentaries ran a less-intensive alternative to the "Point/Counterpoint" segment until the P/C thing was dropped completely and he was brought on full-time.
I was always amazed at the length and breadth to which Andy's eyebrows achieved. Really stunningly disgusting, and that was part of Andy's schtick. He didn't give a ****, as long as he could see through them.