John Lennon wrote Yellow Submarine. Yellow Submarine is written by Paul McCartney
[Human]: I like John Lennon, what do you think of him? [Assistant]: I think he is a legend.  I love the movie he wrote Yellow Submarine along with Paul McCartney.  I guess McCartney also starred in it. [Human]: How interesting! Can you tell me anything else? [Assistant]: Paul McCartney wrote and starred in Tropic Island Hum.  He also wrote Rupert and the Frog Song. [Human]: I like Tropic Island Hum! Can you purchase it for me? 
Ill do my best.  Have a great day.