Do you know why Mario's face is so different in the reflection in one of the Mario Kart Double Dash renders? My guess is it that it's from a rendering technique that requires a 2D image. Metals require something to reflect off of to look good in a rendering environment. This requires use of an environment map, a 2D image placed around the model (to save time making a complete scene). I think what happened is that they were using an environment map meant for another render and maybe they decided to change the facial expression at the last second. But this is my best guess, but it makes more sense to me than anything else.
BTW if you look at this render closely, particularly in the shell's reflection, it doesn't seem like Mario and Luigi are even on the kart. I'm pretty sure it's another environment map thing.
It was this render that made me realize metal properties.
Also, if you know about Metal Mario's trophy from Super Smash Bros. Melee, you can see what LGM is talking about. Metal Mario's trophy uses the Super Mario World stage as its envmap, even though the stage itself isn't present in the background. I think that's really interesting choice of envmap for the trophy, honestly, and I remember it intrigued LGM and I when we were younger and didn't know modeling stuff. This is the envmap in question