A) Made a cameo on Monty Python's Flying Circus: Ringo Starr. Here's his scene.
B) Helped finance a Monty Python movie: George Harrison; when Life of Brian's first financier backed out, worried that the film was controversial even before it was shot, Harrison and his then-colleague Denis O'Brien started Handmade Films -- mainly because Harrison wanted to see the film.
C) Produced a song by Monty Python's most frequent song contributor: Paul McCartney. He helped produce "I'm the Urban Spaceman" by the Bonzo Dog Doo-Dah Band, fronted by Neil Innes -- the guy who contributed songs to Flying Circus, played the minstrel in Monty Python and the Holy Grail ("He was not at all afraid to be killed in nasty ways...") and later co-created the Rutles.
D) Praised Python in an interview: John Lennon. He said so in this segment of an interview.
Now you know. Maybe you knew, so if so, good for you!