When Hellboy II was first envisioned, producers say it had plenty of creatures and most of them weren't even supposed to be rendered in CG. A lot had to be fleshed out using traditional prosthetics, makeup, and the usual costumes and silicon over skin. One of the creature subcontractors, Creature FX says there were originally thousands planned in the script---the movie's secondary title is, after all, The Golden Army.
The studio had to rethink things and ended up toning down on creatures and physical effects. But in spite of the trimming down, it was still one hell of the job for the effects team--- and the actors of course, who had to endure hours of production time waiting in full makeup just in case they were needed on a take. Doug Jones, who played Abe Sapiens was reportedly in full "fish" outfit for 108 days during the shoot.
The effort put in by the effects and makeup people can really be appreciated in the Troll Market scene, where creatures you've never seen before are made to walk, talk, and hawk.
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Interview with Ron Perlman in full Hellboy 2 makeup