Rihanna`s greatest prank: Your sister is pregnant!

London: Singer Rihanna, who has a wicked sense of humour, says that her greatest ever prank was convincing her best friend`s sister that her younger sibling was pregnant.

The singer-and-actress revealed one April fool`s day she and her pal decided to trick her friend`s elder sister into believing she was going to be an aunt, a joke which reduced the recipient to tears.

"Me and my best friend called her big sister to fool it out she was pregnant. There were real tears being cried on the other phone, real panic, real anxiety attacks, it was funny in the end but in the moment we were like did we go too far?" contactmusic.com quoted her as saying.