The scene in the first movie right after Hellboy has killed a monster while holding a box full of kittens. The young lady who owns the kittens comes forward and without caring that this is a huge, red guy with horns, a tail and the word "hell" in his name, she smiles at Hellboy with genuine appreciation, and he pets one of the kittens with the finger of his huge hand.
Lets explain that: Perlman volunteered to do it even though they could have gotten somebody else. He sat through four hours of make-up. The article even suggests (though this is ambiguous) that he personally paid for lunch for everybody there.
No, he sat through four hours just to get the makeup on. It takes another four hours to get it off. He literally sat through eight hours (an entire third of the day!) of makeup work just to make this kid happy. Somebody give Ron Perlman a medal!