Big Show -- John Cena's 'Trainwreck' Junk Is Too Much for Me (VIDEO)

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John Cena naked might be a glorious thing to behold, but his fellow WWE star Big Show draws the line at seeing the man's semi-erect penis on a massive movie screen.

We got Big Show at LAX, and filled him on (spoiler alert) Cena's scene in "Trainwreck" where he shows off a good bit of his championship goods. The big man's reaction is priceless -- at first, he's totally comfortable, but the details of the scene push him over the edge ... in a funny way.

Also comical -- our photog suggested Big Show, who played college hoops at Wichita State, could have taken Shaquille O'Neal back in the day.

Yes, he's a 7-footer ... but every man knows his limit.