Adesugata Mahou no Sannin Musume

Basically this is just showing old footage from the regular series with voiceovers.

It starts with a little comedy bit about the three magical girls (Mami, Persia and Emi) eating a hot-pot, changing their form, and jumping into a hot-spring and saying tongue-twisters.

This is followed by about 20 minutes where they show various scenes from the three shows' regular episodes, but the girls are talking over it as they call their 'boyfriends' and introduce each other.

And, that's about it. There is not any particular reason for anyone to watch this, unless you are ... a die-hard completist. And even then, it's just a boring rehash of what you've probably already seen before.