One excellent way to entertain friends and get yourself into the holiday mood is to download the ElfYourself app. To use it, snap photos of as many as five faces — yours and those of friends and family. Then center the faces in a special frame, add a custom text message and press “O.K.” ElfYourself pastes the faces onto animated dancing elves in a short, funny musical cartoon — for example, a Christmas countdown song that includes kittens popping up in unexpected places. You can share the resulting video on Facebook, Twitter or elsewhere. Be prepared for giggles. The app is free on iOS and Android, but comes with just one video — the kitten one. Unlocking more video themes costs $6, for which you get different music styles like hip-hop or an “Oh Hanukkah” video.