June 24, 2015 10:15 AM EDT

Jon Hamm stopped by Jimmy Kimmel Live! last night and since Hamm wasn’t promoting any particular project, the two friends just chatted. Kimmel did have one burning question for the Mad Men star: why was he on stage at the Bonnaroo music festival throwing gummy bears (“As you do,” said Hamm) into the mouth of Belle and Sebastian’s lead singer Stuart Murdoch? “I don’t know why that’s weird,” shrugged Hamm.

Turns out it was a gag he and Zach Galifianakis had been practicing on the set of their new comedy, Keeping Up With the Joneses. Hamm was bored one day (the movie is being filmed in the suburbs of Atlanta), so he just started chucking gummy bears into Galfianakis’ mouth. When they hit the music festival, they decided to show off their technique to the crowds. Hamm then demonstrated his skills by throwing them into Kimmel’s open mouth.

That wasn’t the last appearance of the gummy bears, though. When Masters of Sex star Lizzy Caplan showed up for her interview, she partook and then started casting aspersions on Hamm for his dry gummy bears. Naturally Hamm had to rush in and crash the interview to defend his honor.

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