I’ve gotta hand it to LUKE BRYAN’s wife Caroline for taking their prank wars to a new level.  On Monday’s “American Idol”, she fooled him by dressing up as a crew member, and being totally obnoxious.

The production crew was in on it.  So was KATY PERRY, and a girl who pretended to be the next “contestant.”  Luke and LIONEL RICHIE had no idea.  The prank started with Caroline “dusting off” a nearby piano and clumsily banging on the keys.

The “contestant” came out and was interrupted by Caroline’s phone alarm.  And when the girl launched into her song, Caroline started crinkling a bag of chips.

And then on cue, Katy left the stage to rip the chips out of her hands.  Caroline followed her to the judges table and took them back.  Finally, Katy came over and ripped the hat off Caroline’s head for the big reveal.

Luke did an “Oh my God” . . . and they rolled tape on some of the pranks the two have played on each other through the years.