Harvey appeared seven times on Late Night and once on Late Show:
1. October 15, 1986
2. January 6, 1987
3. March 24, 1987
4. July 31, 1987, wearing a NABET strike t-shirt. (Linda Ellerbee wore the same t-shirt when she appeared on Late Night a week later on August 11.)
5. November 17, 1987
6. August 31, 1988: Harvey's appearance is preceded by the end of Act 1 (with Biff Henderson and Gerard Mulligan) that then has its callback near the end of Harvey's second segment. Following Harvey is the first few minutes of Dumb Ads, as Dave tries to readjust. Then a few seconds of the next segment with the adjustment still a ways to go. Finally the closing segment, as Dave thanks "most" of his guests.
7. April 15, 1993
8. Late Show: May 16, 1994

UPDATE: re November 17, 1987 (#5 above): I realized too late that I had chosen the rebroadcast, which interrupts the closing act with Bill Wendell's repeat message (it's at 1:08:48). So I've uploaded the segment from the original broadcast, without the interruption, here:    • Addendum to Harvey Pekar Collection, ...