Max's French voice actor (from the '99 dubbing) is Cartman.
Lance Percival, who voiced Paul and Ringo on the Beatles' ABC cartoon show, voiced Old Fred.
Money, Dear Boy: This movie was made solely because the Beatles were contractually obligated to make a third movie. They learned belatedly that, since this was an animated movie that did not quite star them, it didn't count. They did like it enough to make a short cameo appearance, though.
Reality Subtext: When the sub's motor breaks down, George comments that he "knows something about motors." He would, as George Harrison's real-life brother was a mechanic.
The Other Darrin: Peter Batten, the one-time actor who voiced George, was in reality a deserter from the British Army, unbeknownst to the staff of the movie. When he was arrested for deserting, Paul Angelis, the voice of Ringo and the Chief Blue Meanie, stepped in to finish the rest of George's lines.