Is it just me or have Pikachu been becoming thinner over the years? I think I remember old images in the Pokedex having Pikachu being pumper and now its not?

Hmm. Is it possible that you’re from the Kanto region? Kanto pikachu are rather curious specimens, actually. The ones native to Viridian Forest and the surrounding area—as far south as Pallet Town, actually—seem a little meatier than any other pikachu in any other region.

There is, of course, a very reasonable explanation to this: the pikachu of western Kanto congregate in urban populations and are considered to be both wily and adorable. Thus, they have learned on their own that running up to humans and standing on their hind paws will yield positive results in the form of pokémon treats, peanuts, halves of sandwiches, and other edibles.

In other words, pikachu may seem fatter to you if you’ve lived in Kanto and have since left for other regions because only in Kanto has the human population managed to allow itself to be tamed by electric rodents.