I'm no animator, but the volume of the slime seems a lot lower when it's moving up and down than when it's on the ground or at the apex of the jump.
There's also a frame as it starts to fall where the shading switches so that the shadow is on the top right and the highlight is on the bottom left, which is strange.
I like its little 'charge up' for the jump and the way the eyes move higher as it ascends and lower as it descends, though.