Ditty for Messenger is an odd little app to send private messages on Facebook with a funny song and custom text. It makes no distinction between groups and individuals, so you can spend ages exchanging all kinds of messages with your friends.
Although most of the songs in Ditty for Messenger have to be purchased, the app has some that are completely free, like Twinkle Twinkle Little Star, Beethoven's 5th Symphony, and the Hallelujah Chorus, which will play in the background while Ditty sings your text out loud.
The best thing about this app is that your friends don't need to have it installed in order to open the messages you've sent them. Let your imagination fly and compose songs of all sorts. The only limitation on Ditty for Messenger is the number of characters you can type: 70 is the limit, but that's still enough to send a funny joke.