I pranked my friend by messing up the outfit he picked out for the day.
What do you think is the most appropriate consequence for that prank?
A few seconds of free time for my friend who felt embarrassed about his choice of clothing.
While pranks can be fun and done without any ill intent, they still can negatively affect the people who have been pranked and that is wrong. If your friend has been embarrassed as the result of your prank, you should apologize to your friend and explain that you meant no hard feelings. Doing so will allow you to maintain a strong friendship with your friend.
Okay. So what do I do now?
I think you should apologize to your friend for starters. That would help.