Yakit for iPhone (free) is possibly the silliest, stupidest fun you can have with an iPhone and a photograph right now. A bunch of us here at TUAW love this ridiculous app.
You snap a photo or pick one from your camera roll. You then interactively animate one or more mouths in the picture.
The interactive tools are terrific, letting you choose from a variety of mouth shapes or roll your own to match the lip and chin line on a photograph.
The app enables you to record a voice track, adding absurd processed effects for very high and low voices.
The results are hilarious. Once created, you host your video on the YAKiT site and share it via Twitter for Facebook for others to enjoy, mock, or revile.
Go on. Download the thing and start playing.