This was a good one! Smooth battle moves, and transitions. Solid sound effects. Speed lines. All simple means by which to amplify the motions, though it does cut off a bit abruptly at the end...
I assume Luigi just jumping right into the air above the lava is an intentional comedy element more so than just a random end, yet it feels like you need some kind of reaction for the viewer to understand that it's intentional too. Him looking down real quick, or shedding a symbolic drop of sweat, or something such just so you know... then: perfect ending.
I share the sentiment that something like this could use a spotlight too, I wouldn't mind seeing this in a P-Bot Top 5. The animation's simple but effectual, and the entertainment value more important than detail level after all. It's straight up fun; the substance you need to by simple means brighten ones day. Still more substantial than a lot of shorts out there.
Good stuff.
-cd-