Shooting his new flick “Dog Fight” in spooky New Orleans, the laughter suddenly died for funnyman WILL FERRELL when invading “ghosts” freaked him out so badly during nighttime filming in a graveyard that the scared-to-death star fled his “haunted” dressing trailer – and refused to work until producers replaced it!

Revealed My Backstage Spy: “During a break in filming, Will had gone to his dressing trailer to rest, but when he got there, he heard an eerie rattling noise – then strange voices coming from the bathroom!”

At first, Will thought the noise was coming from outside the trailer, but as he went closer to the bathroom door, he was absolutely certain at least one person was in there. He later told co-workers it sounded like people were “having sex in the john!”

In a panic, Will beat it fast and raised the alarm, calling for security to throw the “intruders” out of his trailer. But when guards searched, they didn’t find a soul! “After awhile, Will went back into the trailer – but once again, he heard the weird noises coming from the bathroom,” said the source. “This time, he threw open the door and was shocked when he saw...NOTHING!”

Fleeing outside again, Will alerted a security guard stationed by his trailer, who told him he’d probably heard noise generated by the ceiling fan – but Will told him the fan wasn’t even on.

“It’s ghosts from that graveyard,” Will wailed to the guard, “and I’m NOT going back in there.”

Execs were forced to haul in a new trailer for the actor, who absolutely refused to step foot in the “haunted” one again. OOWOOOOOO!!