Lady Gaga kicked off her “Monster Ball” tour in Montreal, Canada, on Friday (Nov. 27). Gaga brought out opening act Kid Cudi to perform his “Poker Face”-sampled hit “Make Her Say.”

“Who is on my f***ing stage?!” she asked before introducing Cudi. “You listen to me, Kid Cudi. If you’re ever f***ing late to my show again, I’m gonna kick your ass.”