While National "Pi" Day is on March 14 (3/14) and many places celebrate with specials on the more delicious, less-infinite kind of pie, January 23rd is the actual National Pie Day.
So while you can scheme on getting yourself some good pie today, let's salute the tried-and-true use of a pie in the movies: mushing into someone's face. It's been used plenty with Laurel & Hardy, the Three Stooges, Blazing Saddles, and a lot of TV shows.
Did you know, however, the first time somebody took a pie in the face was WAY back in 1909?? It happened in a movie called "Mr. Flip". Here's a clip of Flip, he gets the (seemingly deserved) pie in the face toward the end. And the whole clip is an interesting look back at the silent movie era in itself...