Rereading the wikipedia article on It’s A Wonderful Life, I found some great tidbits:
A popular fallacy began that it entered the public domain and many television stations began airing the film without paying royalties. The film was still protected by virtue of it being a derivative work of all the other copyrighted material used to produce the film such as the script, music, etc. whose copyrights were renewed.
Click here for a more detailed discussion of the issues.
Finally, the article lists some pop culture references to the movie:
The characters in Mystery Science Theater 3000 frequently use lines from It’s a Wonderful Life while riffing the films they watch, such as “Why don’t you kiss her instead of talking her to death!” and “This is a very interesting situation!” Perhaps their most frequent reference is the use of “Out you two pixies go, through the door or out the window!” (or variations thereof) whenever characters in a film are being forcibly evicted. Also, in dogging a short entitled “A Case of Spring Fever,” a man awakens, sprawled on his broken couch, from an alternate reality where springs never existed, and the characters cry out “Merry Christmas, you wonderful old couch!”
(See also my essay on the film)