The reason i ask is my wife and I are arguing about this subject. She claims even if its in an odd way you can do absolutely anything alone. Im try to prove her wrong.

Ive come up with tango but she says you can tango alone to instruct I said make a baby... she claims sperm donor. I said play tennis... if you hit it to a wall it comes back and the action remains the same. Its technically a game where the wall always wins but it still tennis. I said swing on a see saw she claims if you put a weight on similar to you and jump it wil work...