There's a Facebook group that's all about creating improv memes. You might even recognize some of your favorite improv-isms (yes, I made that word up, so it's totally real now; just call me Shakespeare). My favorite so far is this one:
You can create your own meme at Quickmeme.com. After you do, upload it to the group and we'll all laugh and sigh and say, "Oh, so true."