All available known appearances from The Don on Jay Leno's show chronologically throughout the years. Some performances are unavailable or abridged (listed below). Apologies for sound/audio quality - all of these are existing videos on YouTube uploaded by others - a big thank you to those uploaders.

I began the video with what I believe to be most (if not all) of the times Rickles made jokes about or referencing Leno and his Tonight Show hosting status during the final years of his Carson appearances, and Carson's eventual retirement. There are about 3.5 minutes of that and then the Leno appearances begin proper at 3:33, beginning with Don's first Jay Leno Tonight Show appearance on August 2nd, 1994. There is also a singular clip of Rickles on Conan from 2008 discussing Jay Leno also inserted into the chronological order. This adds context to the relationship between the two entertainers.

Personal disclaimer - I think Rickles was obviously at his best on Letterman/Carson/Ferguson/Conan or literally anyone else, Leno is borderline insufferable at times and to the very end (but especially in the 1990s) was often just trying to pettily one-up Don rather than let him shine or do his craft. I think this has a lot to do with both Leno being unfunny and wanting to "prove" his worth to a longtime Tonight Show guest, plus the insecurity that it should have been Letterman's show. But Rickles lovers will have lots of treats inside, just like his relationship with Letterman over the years evolves, so does his with Leno. Additionally, there are a lot of good jokes made at Leno's expense, so if you don't like him, then you have a lot to look forward to.

Anyways, here are 12 out of the 16 known Rickles appearances. If more come forward, then I can always re-upload later.

Rickles' Appearances on Carson Talking About Leno:
0:00 - 10/14/1987, The Tonight Show With Johnny Carson
0:38 - 1/12/1989, The Tonight Show With Johnny Carson
1:38 - 5/31/1991, The Tonight Show With Johnny Carson
2:26 - 3/5/1992, The Tonight Show With Johnny Carson (Rickles' final appearance on Carson)

Rickles' Appearances on Leno:
3:33 - August 2nd, 1994 - 1st appearance
17:51 - August 2nd, 1994 - Rickles sits next to Roger Daltrey (The Who)
19:51 - August 2nd, 1994 - Participates in bullwhipping exhibition post-interviews
[2/10/1995 (2nd) appearance is unavailable online]
24:22 - May 22nd, 1995 - (3rd) Sits next to Courtney Thorne-Smith (first part of appearance unavailable)
30:24 - August 29th, 1995 (4th)
[12/13/1995 (5th) appearance with Meat Loaf and Rot unavailable online (picture here: https://www.gettyimages.com/detail/ne...)]
[2/14/1996 (6th) appearance with Martin Scorsese unavailable online (picture here: https://www.gettyimages.com/detail/ne...)]
41:17 - April 18th, 1996 (7th, contains segment with Roberto Benigni)
56:37 - October 22nd, 1996 (8th)
[5/20/1997 (9th) appearance unavailable online]
1:06:34 - December 16th, 1997 (10th) [segment with Ian Jackson unavailable, picture here: https://www.gettyimages.com/detail/ne...]
1:16:09 - May 11th, 1998 (11th)
1:24:39 - October 7th, 1998 (12th)
1:34:49 - November 26, 2002 (13th) [incomplete footage, cuts in partway through]
1:42:33 - January 24th, 2005 (14th) with Bob Newhart; tribute to Johnny Carson who died the day before. [Very abridged version due to heavy copyright restrictions]

Don Rickles on Late Night with Conan O'Brien
1:43:42 - November 12th, 2008 (short segment)

Back on Leno's show:
1:44:23 - July 19th, 2010 (15th)
1:55:14 - July 19th, 2010 - Sits next to Dwayne Wade (NBA player) [trimmed segment]
1:56:22 - July 14th, 2011 (16th and final known appearance) [segment with Bristol Palin unavailable]


Notes:

2/10/95, 12/13/95, 2/14/96, and 5/20/97 appearances are completely unavailable online.

His 5/22/95 appearance is unavailable except for sitting next to Courtney Thorne-Smith.

His 11/26/02 appearance is only partially available (the tape cuts out his introduction and likely at least a couple minutes of the interview). After his interview, Rickles sits next to Eddie Izzard but I did not include it, it's not interesting & has almost no Rickles contributions.

Rickles' 1/24/05 appearance with Bob Newhart exists in full on YT in parts, uploaded by Gregory Papadoupolous. Heavy copyright exists for that specific episode for some reason, but it's out there and worth seeking in bits and chunks for the die-hard Rickles fans.

His appearance on 7/14/11 had him sitting next to Bristol Palin and allegedly making a couple jokes at her and her mother's expense (recap found here: https://www.vulture.com/2011/07/last_.... Unfortunately, that portion is unavailable online.