Grass. Frogs. Avocados. Emeralds. Shamrocks. Broccoli. The Incredible Hulk. Puppies? One of these things is definitely not like the others!

According to The Sun U.K., one lucky green puppy was recently born to a Golden Retriever named Rio in the town of Golspie in the Scottish Highlands.

The pup was named “Forest” by her owner, Louise Sutherland, due to her uniquely colored fur. Forest is one of nine puppies, all the rest of whom have completely normal fur.

“The first pup was stuck, so myself and my daughter Claire managed to free him and pull him out safely,” Sutherland told The Sun. “It was all hands on deck but then as the puppies started to arrive, we noticed that one of the puppies had green fur. We couldn’t believe it.”

Sutherland had every right to be stunned: the occurrence is so rare, it’s only known to have happened three other times. According to a 2014 article in TIME, veterinarians believe that exposure to biliverdin — a green bile pigment found in the placenta — may be the cause.

“The color has faded quite a bit already and will be gone soon, I’m told,” said Sutherland, and the TIME story backs this up. Apparently the condition tends to resolve itself within a few weeks.