The Jerk:
When Steve Martin tells Bernadette Peters that her skin looks so soft and...may he touch it. Whereupon he gingerly approaches, then pinches her cheeks and yanks them in various directions, saying "Yeah, it has a lot of resilience and flexibility like I thought."
You could tell Bernadette could barely hold back from giggling herself.
"The new phone books here,
the new phone books here."
"Things are going to start happening to me now."
"The new phone books are here!"
"...and this chair... and that's all I need..."
Great Movie.