I'm going to cuddle with my friend's crush in front of him.
Why would you do something to hurt your friend?
I'm bored, and I want to see how he reacts.
Being bored is not a reason to get involved with someone your friend has feelings for. Your friend will see your actions as a betrayal and will feel very hurt. You cuddling with their crush will put a huge strain on your friendship and may even end it.
I'm not interested in talking to him anyway, respect is earned not given.
If you don't like your friend you can just end the friendship instead of hurting him like this. There is no reason to use his crush to entertain yourself. If you're so bored get a hobby or something.