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Since the inception of the series, the iconic Pokemon known as Pikachu has been known as a “mouse” type. Now, we’ve learned the electric ‘mon was actually originally based on another rodent.

The news comes via a new interview (via Yomiuri) with Game Freak designer Atsuko Nishida, who is the original designer behind the yellow and lightning-infused creature. “At the time I really liked squirrels,” she said.

She continued on the mon’s design. “I wanted the creature to have puffy cheeks, squirrels also have cute tails, so I definitely wanted it to have a tail. However, I also wanted the character to have the lightning element, so I shaped the tail like lightning.”

Nishida said that at the time, she didn’t have a pet squirrel – but she definitely wanted one. “Squirrels weren’t popular then. I like animals and back then I had both a ferret and a turtle at home. Because I liked how squirrels have silly and cute antics, I wanted one.”

The Pikachu designer also noted squirrels uncanny ability to stuff their cheeks with food – as opposed to how hamsters can stuff themselves round, thus leading to the points on its cheeks.

She noted that when the Pokemon was named “Pikachu,” it was then designated a “mouse” type, with Pokemon creator himself Satoshi Tajiri coining the term “Electric Rodent.” Later, when the first TV anime based on the series debuted, Pikachu had another design change.

The latest games in the franchise, Pokemon Ultra Sun and Ultra Moon, are now available for Nintendo 3DS. In related news, a new mainline Pokemon game is planned for Nintendo Switch.