"Supergirl" borrows a line from "Superman II"

In the four-part superhero crossover saga called "Crisis on Earth X" just aired on the CW network (which was very well done and had several moments of believable peril, as well as emotional drama), many of the characters had to confront their lookalike alter-egos (or doppelgangers, if you prefer) from the alternate universe.  And there were a ton of "Easter eggs" and homages to movies and TV shows from the past.

This one was my favorite.