Rihanna loves playing pranks on her friends. 
The 'Umbrella' singer is so obsessed with tricking her pals she has to play a joke every hour.
Rihanna said: "I really like playing pranks on people. I do that a lot. Every day is a new one. Actually, every hour! It's almost second nature to me.
"I play pranks on people, trick them, tell lies and push them in the waterfall! It's a way of adding fun to my job and my life." The 19-year-old star also said she is fulfilling the title of her first album, 'Good Girl Gone Bad'. She added to FHM magazine: "Let's just say I want to do things my way. I can be stubborn. If someone wants to force me to do something, I'll end up doing the exact opposite.
"I have to be myself. If I want to be sexy, I mustn't restrict myself. I want to be young, fun and sexy."