The Co-op supermarket has asked customers who bought their chocolate Easter bunnies to bring them back, after a battery was found inside one.
They're worried that there could be more batteries hidden in other chocolate bunnies, which could be very dangerous if someone accidentally ate them.
A girl in Nottingham found the small round 'button' battery when she bit the ears off her chocolate bunny.
She wasn't hurt because she didn't swallow the battery, and told her mum straight away.
Even though they're small, batteries can be very dangerous to swallow.
They can get stuck in your throat, and the chemicals inside can burn.
A spokesman for the Co-op said: "The health and safety of our customers is uppermost in our minds.
"We are concerned about one incident of alleged product tampering involving our hollow milk chocolate Easter bunny foil figure, which has been found to contain a small battery inside."
Co-op say that about 3,000 chocolate bunnies have been sold around the UK and they are warning customers not to eat them, but to bring them back and get a refund.