The very, very end of the movie: Tanner, Lela, Butchy, CheeChee, Seacat and Giggles suddenly find themselves in the "real" world and bump into a surfer. The surfer shows them an iPhone with a picture of Justin Bieber. The reaction of the 1960s characters is priceless.
Mack's facial expressions are priceless; one of the best examples was the scene with Meant To Be.
Mack in her biker gear is hilarious because you can tell how uncomfortable she is in it.