While it's often called an electric mouse, Pikachu looks like nothing of the sort. The iconic face of Pokemon is one of the cutest things thing ever made for entertainment, so the fact that it has been associated with mice has always been a bit odd. Unsurprisingly, one of the designers of Pokemon has revealed that Pikachu is not based on a mouse.
The adorable electric-type Pokemon is actually based on squirrels. Why? Because former Game Freak employee Atsuko Nishida really liked squirrels at the time. No really.
During an interview with Yomiuri, Nishida revealed that she was really into squirrels at the time and she wanted to make a character with the creature's puffy cheeks and cute tails. The tail would end up being shaped like a lightning bolt since it was an electrical-type and needless to say, it worked out in the end as even those who barely follow Pokemon know Pikachu.
Squirrels also helped Nishida design how Pikachu would store electricity, noting how squirrels often stuff their cheeks with nuts. Pikachu's thunder attacks almost-always come from its cheeks, so this ended up helping the Pokemon establish an identity.
Oddly enough, we don't know why Pikachu was dubbed as a mouse-type Pokemon afterward. At the least, Nishida created the face of a million dollar franchise and she should be proud of that.