Channel Hop: From ABC to ESPN. As both channels are owned by Disney, this is only a jump from broadcast to cable.
Practically, however, it was a wholesale change, as much of ABC's old production crew (including the entire commentary team and the lead producer and director) were graciously allowed to leave for NBC, while ESPN's old Sunday Night Football crew formed the backbone of the new MNF production.
Hey, It's That Guy!: Among the familiar faces that pulled MNF duty: AlexKarras, O.J. Simpson, Joe Namath, and Fred "The Hammer" Williamson (who proved to be so bad he was replaced during the pre-season).
The Pete Best: Keith Jackson. When Frank Gifford was unavailable during the first season, executive producer Roone Arledge hired Jackson for the play-by-play. When Gifford became available, Jackson was unceremoniously fired. According to the book Monday Night Mayhem, Jackson didn't even know he'd been dumped until media reporters called him, asking for comment.
In contrast with many Pete Bests, however, things ended up working out for Jackson, who went on to a long and prominent career as ABC's lead college football voice.
What Could Have Been: Such well-known announcers as Curt Gowdy, Vin Scully, and Jack Buck were all offered the MNF play-by-play role prior to the first season, and all turned it down for various reasons. (Buck did, however, end up calling Monday night games for many years...on CBS Radio.)
NFL Commissioner Pete Rozelle originally wanted CBS to get the Monday night package; giving them right of first refusal, only for CBS founder William Paley to nix the package due to potentially disrupting their strong Monday night lineup. NBC declined due to airing movies on Monday night; allowing for last-place network ABC to get the prime-time lineup.