I've been high once. Entirely off of peer pressure and it was one of the worst feelings ever. I entirely wish I never did it. I entirely wish me "friends" wouldn't have pressured me so hard. I no way am I happy that they did.
Secondly, I had another "friend" try to sneak a shroom stem into a reese peanut butter cup once. I bitched at her and called her a shitty friend.
Third, I have been roofied and thank god I had really good friends around me to take care of me. I was enfuriated by who ever did it. I don't know how it happened, but it happened. Maybe smoking out the room isn't quite as bad, but I'd put it in the same world.
Just cause you think your friend is uptight doesn't mean drugs are the way to break that. Get him to live a little. Sneak into a hot tub, convince two girls to go home with him... there are other ways.
If my friends tried this on me, i would seriously reconsider my friendship because my friends have enough respect for me to not do this.
I know you think its a harmless prank, but you never know the reasons why someone is really doing something. Maybe his uncle is a drug dealer or he has a friend in jail for dealing. You don't know. Don't do it.