The pair joined the panel of the pop star search show this year and Lovato said they quickly bonded over tic tac toe and doodle, reported Popel magazine.
"We bonded at 'The X Factor's boot camp. During breaks we'd sit behind the panel and use the paper to play tic tac toe and doodle," Lovato said.
The singer also said that she loves to play pranks on her staff.
"I do little ones all the time. When my make-up artist is going my makeup, I like to scare her when she is really focused. I jump back in my chair and she freaks out. It's actually not very smart because it can totally mess up what she's doing," Lovato added.