Snopes has an article published on this picture, and frogs in salads, in general. I had expected it to be Photoshopped, but it doesn't mention any Photoshopping in there. It's gotta be a hoax, though... the poor thing would have suffocated. Funny, though.
http://www.snopes.com/photos/animals/frogsalad.asp
"no conclusive determination has been made about the incident; whether (as often happens) the animal was deliberately placed in the package by the consumer as a hoax, whether someone introduced it into the package after production as a prank, or whether it was trapped in the bag during the production process."