I was wearing my Cthulhu shirt today and my 3yo son asked who it was. He's big into the (Lego) Marvel Pantheon at the moment, so I explained he was a super duper villain. My son immediately suggested Hulk might punch him.
I don't know if Hulk ever did a Cthulhu crossover. Batman surely did, but I feel like Marvel doesn't like anything unexplainable.