Mark Hunter was just about to tuck into his second mouthful of the popular brand when he spotted the mouse.
"I saw this dark shape appear in the milk, but I didn't realise what it was until I fished it out with my spoon," he told the Mirror.
Mark, a psychology student from Maida Vale, London, dried the mouse off and phoned the cereal's manufacturer Kellogg's. They promised to collect the rogue rodent and send it to the University of Liverpool to try and ascertain where it came from, and how it ended up in the Rice Krispies.
Paul Wheeler, a spokesman for the brand, said it was an 'extremely rare' incident that would be thoroughly looked in to.
"We are devastated and will be investigating fully," he added.
Ugh! How disgusting? Wonder if Mark will be sticking to toast for breakfast from now on?