Muffin was a dog belonging to Terry McCarthy when she went to Packanack Lodge Counselor Training Center in the summer of 1984. Muffin was loved by her owner and wore a purple ribbon on her head. Shortly after arriving at the Training Center, Muffin encountered backwoods killer named Jason Voorhees while exploring in the woods. Later that day, Sandra Dier and Jeff Dunsberry found the carcass of a dog that looked suspiciously like Muffin, although this was not, because Muffin is showed to be alive at the very end of the film, meaning that the dog being found by both Sandra and Jeff was not their beloved Muffin. That night, after surviving Jason's first killing spree, Ginny Field had been reunited with Muffin, though this is highly suggested to be a dream sequence.
An elaborate explanation of the ending is given in an interview with Peter Bracke, author of Crystal Lake Memories: The Complete History of Friday the 13th, in the Friday the 13th Part 2 DVD features. There he reveals that there was an unused ending in the movie. After Ginny questions where Paul is, the scene switches to Mrs. Voorhees' head, which her eyes open and smiles wickedly, indicating that Jason had killed Paul in cold blood. But when they filmed it, they thought it looked too silly and cut it from the film. This being said, Paul's actually fate is left up to the imagination of the audiences/viewers.
- Since Jason's never been seen hurting or killing innocent animals, unlike Michael Myers from Halloween film series (for example), it could be that he left Muffin alone, as he only kills people who gets in his way.
- If Muffin was spared, she may have ran away during the struggle with Jason. It is possible she returned and could have been found by one of the training camp counselors or the police personnel; given to someone who knew Terry or Terry's closest kin, or simply she ran off from the struggle and was adopted by a new owner.