Grab a smartphone or tablet and open a video recorder. Play a video of your own selection from a tv, another tablet or another phone, but turn the volume down all the way. Film the screen and produce the soundtrack with your own mouth. You can do sound effects and speak all the voices for the characters in the video. Use your imagination and make up crazy and funny sounds and words for the characters.
Show or send your movie with new sounds to your friend. Ask your friend to make same kind of movie for you.