Young Frankenstein
Mel Brooks is also open to adlibbed lines in his films. This was how the “What hump?” line founds its way to Young Frankenstein. Marty Feldman delivered it off the cuff and it worked well for the film!
Animal House
It is no secret that Animal House was full of amazingly talented people. Almost all the cast members had experience with improv and they used it to their advantage. This was true for the main character himself. The entire “I’m a zit” cafeteria scene was all John Belushi.