So in a previous post I made some size charts for the Mario cast to figure out how tall they all actually are.
If you have seen it I put King K. Rool as pretty big in comparison to DK.
Now I actually underestimated his size, he is much bigger.
Now a lot of people think K. Rool is around the size of DK because of his non-canon Smash Bros. appearance. But he is far bigger than DK.
In his first appearance he was already depicted as huge in comparison to DK, but with the limitations of pixels. Eventually in Donkey Kong 64 his full size is truly realized as he is massive compared to the Kongs and other kritters. Heck put him next to Bowser in his base form, and he would tower over the King of the Koopas.
This size is remains consistent as in Donkey Kong Banaza he retains his massive size.
Now he likely eats something like a Mini Mushroom or uses some times of size altering method to make himself smaller to participate in events such as Mario Super Sluggers. It's not like he hasn't altered his size before, we seen him make himself giant in DK: Jungle Climber by eating a Crystal Banana.
And outside of Mini Mushrooms, the Mushroom World is in no short supply of shrinking methods. Just look at the the Sky Crystals.
Written by Eris the Lorekeeper