The Stay Puft Marshmallow Man is one of my favorite designs & is genuinely one of the best practical effects that still hold up to this day. The cartoon version is also very good.
I really like that he goes from being happy to looking evil. The way he slowly moves around & how his eyes look back & forth. His marshmallow can also be slightly roasted or burnt. His cartoon version is also very goof.
He's a very powerful joke Kaiju despite his fun appearance. Its controlled by a deity with few ways of defeat, he can even take small pieces of himself & make mini fire-breathing minions.