This is one of those scenes that starts off with a bit of a story. It's a funny opener. Funny.. that is until someone loses a load. It was a takeoff on the breast-expansion fetish.
Emily Anderson buys a jar of breast enlargement cream that allegedly works overnight. She shows her man the jar of breast cream she has rubbed on her tits. He tells her that the stuff will never work and goes to sleep.
When he wakes up, he sees that Emily's top has come unbuttoned because her big tits have burst it open. She is now the proud owner of huge boobs.