Anyway, we know that M*A*S*H and Hogan's Heroes were pretty much rival sitcoms (even though they were of different decades), but there were a LOT of similarities between the two, even behind the scenes; here are a few examples I can think of off the top of my head:
- We know that Larry Gelbart, Gene Reynolds, and Burt Metcalfe didn't want M*A*S*H to have a laugh track, but apparently they tried to get away without one on Hogan's Heroes as well: the story goes they produced two prints of the original pilot episode, one with a laugh track, and one without, and when they tested it with audiences, those watching the laughless version were left confused, but the version with the laugh track succeeded, so they made sure Hogan had a laugh track.
- Speak of whom, both shows had a lot of the same crew behind-the-scenes, including: Gene Reynolds (producer/director), Laurence Marks (writer), William Jurgenson (cameraman), and others.
A number of M*A*S*H actors had also appeared on Hogan's Heroes, including: Bill Christopher (who was a regular character replacement for Larry Hovis), Bernard Fox (recurring role as Colonel Crittenden), Roy Goldman (a background POW for all seven seasons), Johnny Haymer (Zale) John Orchard (Ugly John), Jack Riley (original Kaplan the Dentist), and Robert Hogan (Smilin' Jack) have all made guest appearances on Hogan beforehand.
- There were similarities in episode plots as well: both shows had a boxing episode (M*A*S*H had Trapper being suckered into a boxing tournament in a bet to get Nurse Cutler back, Hogan's Heroes has Kinchloe being suckered into a boxing tournament to keep the Krauts preoccupied during a scheme); both shows had a Dear John episode for the arguably most naive character (M*A*S*H having Radar get a Dear John recording from his fiancee now engaged to Elroy Fimple, Hogan's Heroes having Carter get a Dear John letter from his fiancee now dating an air raid warden).
- Some would argue there are similarities between the characters of Colonel Blake and Colonel Klink, which I can kind of see: both are bunglers, and not very good commanding officers, while others take advantage of their incompetence for their own benefit (Hawkeye and Trapper scheming using Henry as a pawn, Hogan and his men scheming using Klink as their pawn)... I see similarities between Hawkeye and Hogan: both are sly and witty schemers, and both are tremendously big ladies men who have on-going affairs with various different women.
- Both shows have biopic connections: there was a biopic about Bob Crane and his fall into pornography obsession, meanwhile there was a biopic about Allan Arbus's wife Diane.
I know there's others, but those are the only ones I can think of right now.