Monster and donkey transformation. This is from Fawcett Comics's Ibis the Invisible #1, but the characters are from a sub-strip titled 'Sir Butch'. The story and art is by Dave Berg and it's a humorous fantasy adventure thing. It can't be the characters' first appearance, based on the dialogue, but I don't know where Sir Butch came from or what other books he appears in. But, point is, Butch and his partner cross the villainous Floda Reltih (get it?) who starts transforming them. It doesn't last long, unfortunately; the poet Button Hookin Button (I don't get what this is referencing) has a counter-move. You can see this scene from https://comicbookplus.com/?dlid=16622 page 47, or read the story from the start on page 46.