It's a whopper of a prank that could lead to felony charges.
Calls have been coming into fast-food restaurants in several states, leading employees to break out the windows.
The prankster frames it as a gas emergency and the only way to vent the store is to smash all the glass.
At least three Burger Kings, one Wendy's and one Jack in the Box have fallen for the prank, or to copycats.
On Friday, workers at a Burger King in the Minneapolis suburb of Coon Rapids, Minnesota, smashed windows of the store after a caller convinced them the place might explode, police Capt. Tom Hawley told CNN.
Employee Ethan Grewe told CNN affiliate WCCO that he was unsure of what to do.
"I guess I was a little scared. My other co-workers were doing it, so I just followed along," Grewe told the Minneapolis-based station.
Someone called the restaurant Friday night, claiming to be a fire department official. The caller asked for the manager and said there was a dangerous explosive gas inside the building and that they needed to relieve the pressure by breaking the windows, Hawley said.
"The employees ran out to their cars and got tire irons to break out the restaurant windows. About 20 windows were busted out," Hawley said.
When officers arrived, employees were very upset, particularly the manager, who had been on the phone with the caller for some time.
"He (the caller) was very convincing. He seemed to have knowledge of fire suppression systems and acted like he was monitoring the building remotely," Hawley said.
There have been similar incidents in Arizona, Oklahoma and California. "We are touching base with (some) jurisdictions to see if they are related," Hawley said. "Whoever did this could be charged with several things, including felony terrorist threats and felony criminal damage to property."
Natural gas leaks can be detected by smell that some compare to garlic or rotten eggs.
CNN called Burger King's corporate office Saturday but didn't receive an immediate comment.