snowclone
A formulaic phrase that can be customized to fit a variety of contexts.
I stumbled upon the site the other day, when I was looking up the origins of the "Im not an X, but I play one on TV" snowclone.
Where it comes from
Blend of snow cone + clone, in reference to the phrase “If Eskimos have dozens of words for snow, X have as many for Y” (which is an example of a snowclone). Coined by American television writer and economist Glen Whitman in January 2004, in response to Geoffrey Pullum on the blog Language Log.
Adapted from the Wiktionary entry snowclone (CC BY-SA 4.0).