Gunnar Boettcher, 20, a Gustavus Adolphus College student, said he was working in his father's Mankato garage when he first spotted the rabbit, which bears growths on its head that make it appear to have a series of horns, the Free Press of Mankato reported Thursday.
Boettcher and his brother, Zander, managed to capture video, which Boettcher narrated in the style of late Animal Planet star Steve Irwin.
"We started filming just for us, just to be funny," he said. "Then we decided to put it on Facebook and it got a lot of views.
"I used to watch Steve Irwin when I was little," Boettcher said. "I was just being a goof, just for me and my brother's entertainment."
The video became popular on Facebook and a friend posted it to website Reddit, which helped it quickly amass more than 200,000 views and nearly 2,000 comments.
Boettcher said he disagrees with commentators who say he should capture the rabbit, which he dubbed "Frankenstein," to get it medical attention.
"It's a great idea to try to help him and make him healthy again, but it's a little ridiculous to blame me for not helping the rabbit and taking him to the vet when it's a wild rabbit," he said. "It's turning into a thing on animal rights. People are saying I'm mean for making it humorous, but it was just supposed to be something fun between me and my brother."
Boettcher said his research indicates the rabbit is suffering from a type of cancer caused by a contagious virus. He said the rabbit is unlikely to live much longer.