Pokémon - Little Ash

Anime has different sized charizards, so I guess Ash's is just bigger than average.

They must've been bred to be larger over the years and only the biggest are chosen to be ride pokemon. The 5 foot is probably just the average the way people are on average around 5 foot 6.Which means somewhere in the pokemon world there are teeny tiny charizards only like 3-4 feet tall or less.