Cool swapping mechanic. Thought it a little awkward to switch between the two characters at first, but once I got a hang of it, it was fun to use. Good use of assets; the game has a fun visual style. The jump feels good, too.
I think the game would benefit from having more sound effects. Aside from jumping, picking up coins, and the background music, the game is mostly silent. Having sounds for jumping on enemies, switching between the characters, and falling in a pit, for example, would add a lot.