Newton's Cradle Cup

When a man performs a Newton's Cradle with a pair of breast. He sticks his head inbetween and lets them hit his cheeks

Zach: how was that lame Barmitzvah.
Derek: it wasn't lame, Lassie let me perform Newton's Cradle Cups.

Zach: she's like a D Cup!
Derek: I know, I got a concussion