Casper meeting up with his cousin Powerhouse, who's identical from the neck up but who's a mighty musclebound ghost underneath. The story originally appeared in Casper the Friendly Ghost #10 in 1959, but where I encountered this was one of the American Mythology Casper's Capers books --- number 3, specifically --- which runs some new and some reprint Harvey content. (I think, from the table of contents, this issue is all reprints, it happens.) So the original art is, let's guess, Warren Kremer and if it's not it's Howie Post.

Anyway you'll never guess what happens with two characters who have the same face but different physiques, unless you know anything about comic narrative!