Sounds like Indiana Jones oughtta whip the butt of young “Kingdom of the Crystal Skull” co-star SHIA LABEOUF, who triggered a big stink during location filming of new flick “Transformers 2” when he snuck a cigarette in the men’s john at the Smithsonian National Air and Space Museum – setting off blaring smoke detector alarms!

LaBeouf snuffed the cig just as museum guards burst in – but they spotted his soggy butt floating in the toilet bowl.

He endured a stern lecture, topped by a warning he’d be ejected from the museum if he lit up again.

The kid lucked out: In February, he was nabbed for illegal smoking on a Burbank sidewalk and fined 500 BUCK$$!

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