Try this one out sometime:
You lie on the mat, your partner straddles over you. Hold each other by the wrists. Alternate doing the following: your partner (still holding your wrists) lifts you up from the ground (sort of like a deadlift). You (still holding your partner's wrists) do a pull-up. Five times each. Immediately after do 10 push-ups. And 25 squats right after that. Then switch roles - your partner lies on the mat and you are straddled over your partner. Do that thing with the lifts/pull-ups again. And the push-ups again. And the squats again. Switch again. Continue doing this for 20 minutes. Try to get as may rounds in as possible.
Good fun :-)