Continuity mistake: During the interview, while sitting, his striped pants are unzipped for a few cuts, then they are zipped in later shots.
Continuity mistake: When Jack is at Deborah's California place talking to her on the couch her arm swaps from raised to lowered between shots.
Continuity mistake: When Deborah tells Jack he must go to LA to make a ton of money his right arm is extended or not depending on the shot.
Continuity mistake: Before Jack plays "Let It Be" for his parents, he talks to his dad who is holding a coffee mug. His left hand goes from holding the mug to down at his side in the next shot.
Continuity mistake: During the performance of "Help!" on the rooftop at the beach, the weather changes from cloudy to sunny (and vice versa) instantly in different shots.
Answer: Believe it or not, the Beatles did not invent the idea that a submarine could be yellow, and yellow toy submarines were sold for children to play with.