Yep! Normals control how a model is lighted up. You can either fix the seam by welding verts together or average normal display. It's a different functionality for each program, I know how to fix via Maya and Max, but I don't know Blender. It's the same terminology though, so if you do as I suggested and search how to average normals/mesh display with Blender, you can find out how to do it with Blender.
Pointed out by youtuber Desbug, Yoshi's looking very down in Mario Party 5's Card Party.
To which I say, why's Yoshi so sad???!
YOSHI HAS RESTING SAD FACE.
Note: The expressions do not change, and everyone else looks happy or neutral.