Voice cast reveal. Scroll to last picture. Lots of Smith friends.

https://www.instagram.com/p/B8jxvF9lrOq/

Hamill as Skeletor, Kevin Conroy as Merman, Jason Mewes as Stinkor and Alan Oppenhiemer as Mossman. Hamill as Skeletor is not really a surprise. Been rumored for quite a while. It does seems like kind of an awful waste not to have Oppenheimer as Skeletor or Merman but at least he is involved.