I think if you are truly aiming to replicate the Undertale style you are best starting with a blank sheet. Undertale sprites are angled very straight. What that means more specifically is that we are not viewing the character from above but rather at eye level. The Bowser sprite from M&L is more of a bird's eye view. We can't change that sprite to the correct perspective so it would need to be sketched out and drawn from scratch.
I also wonder if Bowser should have a smaller head to better fit that style too. Incidentally, did any Undertale sprites have that many bright colours at once? So many questions...
I also wonder if Bowser should have a smaller head to better fit that style too. Incidentally, did any Undertale sprites have that many bright colours at once? So many questions...