If you know the story, you know the stats—the eponymous character of Dr. Seuss’s "The Grinch Who Stole Christmas" starts the tale with a heart “two sizes too small” and ends it with one three times larger, thanks to Cindy Lou Who and her friends.

Though he’s never diagnosed a fictional character before, Johns Hopkins cardiologist David A. Kass, MD, said in a release from the university he immediately assumed the Grinch suffered from heart failure, since heart failure patients often have weak, enlarged hearts.

“But, if you have heart failure, you’re not going to feel good; you’re not going to be smiling; you’re not going to be lifting your sled, as I understand he did,” Kass said in the release. He also ruled out a ruptured heart before coming to his final diagnosis: The grinch is a snake.

Snakes—pythons in particular—are known for having hearts that grow and shrink with meals, he said. Combined with the grinch’s color, it just makes sense.

“We know he’s a snake—he’s a snaky-like kind of guy,” Kass said. “Now whether it was triggered, in this case, by a meal, I can speculate. As I recall, he goes down to Whoville, and he’s going to stop Christmas so he’s getting all the presents, like reverse Santa Claus. But he gets all the food, too. He gets that roast beast, and I don’t think he just threw it in his bag, so maybe like our python, that turned out to be a rather big meal. And sure enough, as he’s going back up, the heart starts getting really big.”

Read the rest of Kass’s theory—as well as scientific explanations for Scrooge’s time travel and Rudolph’s glowing nose—on Newswise: