R+b star Ciara was forced to perform at a recent in-store signing with mustard oozing out of her shoes after rapper Yung Joc played a practical joke on her.

The pair has been touring together on the Screamfest '07 tour and prankster Yung Joc - real name Jasiel Robinson - has been catching the Goodies singer out with pranks at every stop.

And he insists his mustard gag is the best to date.

Yung Joc explains, "Me and T-Pain put mustard packets in her shoes. She was doing, like, a live in-store in with the kids and this little girl said, 'Ciara, you've got some yellow stuff coming outside of your shoes.'"

But Yung Joc admits he has been on the other end of some tour shenanigans too.

He adds, "I'm gonna have to get T-Pain and Lloyd back... I'm gonna have to fire my security 'cos he let them in my hotel room while I was sleeping; I woke up with a toothpaste hairline."