OK so I got no idea if you understand Finnish or not, but a big bunch of years back someone did some cut and paste with some old Finnish moomins episodes, resulting in a whole new plot and story about Moomintroll and Snufkin. Don't want to spoil too much, but a gender reassignment is included. You can find the whole saga here, though the quality's kinda crap: 9sCw03DEm3c Otherwise each of the 3 episodes can be found on YT individually with the title 'Yksinäiset vuoret', lit. 'Lonely Mountains' in Finnish. If there's a language barrier, I hope you can find some subtitles or other translation.