[DrKMcK]

Hershey's chocolate bars come in both milk and dark varieties. Chocolate can kill, so definitely check the entire cage for stashed chocolate. I'd also have the vet check him as soon as possible. A half square of chocolate for a hammy is too much. If your siblings do this type of thing the cage needs to be placed out of their reach. If they are old enough to know better, a conversation with your parents about this is in order. I hope your furry is okay.