The two actors participated in a game called "Playground Insults," where they were asked to essentially say really rude things about each other.
Needless to say, it got real very fast, especially when Robbie acted like she hadn't heard about one the greatest television shows in American history.
Poor Will was taken aback, unable to come through with a witty reply.
But Margot had no trouble at all.
After some time to mull things over, Smith finally hit Robbie with a burn.
And if her reaction is anything to go by, Will's comment had her shook. Priceless.
Unfortunately for Smith, his moment of victory was short-lived because Margot hit him back with the ultimate put-down.
The two stars continued to take cheap shots at one another, with Margot ultimately winning the game.
And thankfully there were no hurt feelings. The two stars still get along famously.