When Jules and Grayson are dancing to Enya she motions slapping him across each side of his face, which was part of Ross and Monica's "routine" on Friends.
On the college campus, Jules tells a girl that the time is 4:20. 420, 4:20 or 4/20 (pronounced four-twenty) is cannabis culture slang for marijuana and hashish consumption, especially smoking around the time 4:20 pm.