The ‘Pac Man Frog’ is a name given to the Amazon Horned Frog, which is described in the article linked to below. This frog will eat almost anything smaller than itself and then some (or at least try and eat some things bigger than itself).
For more visit:
http://animals.nationalgeographic.com/animals/amphibians/amazon-horned-frog/
Kevin's Walk on the Wild Side 