They may have taken on the forces of darkness in their respective superhero films, but now Chris Pratt and Chris Evans may have to take on their hardest task yet: humiliating themselves after their American football team lose in the Super Bowl.

Thanks to some escalating trash-talk on Twitter, the pair have set up a wager: if their team loses, they must visit a children’s hospital in the winning city dressed in their full superhero garb, plus the winning team’s colours. For Pratt, a Seattle Seahawks fan, this would be his Star-Lord from Guardians of the Galaxy; for Evans, who supports New England Patriots, it’s Captain America.

It all started when Evans cast the first stone:

Well, well, well @prattprattpratt, looks like our teams are going into battle. For the next 2 weeks, you are not my friend, you are my enemy — Chris Evans (@ChrisEvans) January 19, 2015

@ChrisEvans We both know there's only one Captain America and his name is Russell Wilson. #SuperBowlBound #LOB #Repeat — chris pratt (@prattprattpratt) January 19, 2015

Evans then responded to Pratt’s taunt, setting the wager in motion:

@ChrisEvans OK. Seahawks win you fly yourself to Seattle, visit @seattlechildren hospital as Captain America, waving the 12th man flag. — chris pratt (@prattprattpratt) January 21, 2015

The ‘12th man flag’ is, humiliatingly if Evans loses, the flag raised at Seahawks games to acknowledge their fans. Evans accepted the challenge, with the caveat that Pratt wear the shirt of Patriots quarterback Tom Brady to his own hospital visit if he loses:

@prattprattpratt I accept. And when the Patriots humiliate your seachickens, I expect Star-Lord to arrive at @chris_haven in a Brady jersey — Chris Evans (@ChrisEvans) January 21, 2015

One of them will be bringing the outfit out of Marvel’s wardrobe come 1 February, when the Seahawks meet the Patriots in Super Bowl XLIX in Glendale, Arizona – the Guardian will be liveblogging the game as usual.