Viral photos have inspired a fluffle of unflattering nicknames, including "Frankenstein bunnies," "demon rabbits" and "zombie rabbits."

Colorado Parks and Wildlife say rabbits in Fort Collins are infected with rabbit papilloma virus, causing horn- or tentacle-like growths.

As weird and concerning as they appear, the virus that causes the dark, wart-like horns or tentacles to grow on cottontail rabbits is relatively common and usually not anything to worry about, CPW