Jet-Lagged 'Captain America' Stars Chris Evans & Anthony Mackie Get Into Insane Giggle Fit

Were the actors jet-lagged? They totally broke down at D23!

Captain America: Civil War co-stars Chris Evans and Anthony Mackie have been spending so much time together that the duo have their own inside jokes, and one of them put a pause on ET's interview at Disney's D23 Expo.

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"I wouldn't have said 'y'all.' I would've been like, 'You guys!'" Evans told Mackie during our interview.

The joke, seemingly apropos of nothing, sent the two action stars into a giggle fit that we'll blame on their long flight from Germany. They had just flown in from filming the Marvel franchise's third film.

"Sorry, that's an inside joke," Mackie explained.

Evans told People that after working together so much, they have an "aggressive inside joke."

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"We just make fun of each other," Mackie added.

Captain America: Civil War opens May 6, 2016.