Release the Kraken!
Sorry, just in a thread on Harryhausen it needed to be said. Apparently, he called his craft 'dynamation'. Imagine all the work that went into his creations, which were often complex beyond what was needed. The Kraken above has four arms, when two would have worked - but Harryhausen seemed to want to go above and beyond. The skeletons in Jason - there are several of them, and the scene goes on for some time. In Golden Voyage, there is the 6 armed statue of Kali when he could have just animated a 2 armed statue of some other god. Nope. Even how he does the Colossus in Jason, where he actually wants the giant statue to seem slow and ponderous, works.
Clash of the Titans really got the brass ring though. Timing wise, 1981 hit a sweet spot when Star Wars said movie goers like fantasy, Dungeons and Dragons was a big thing, and before a couple of films failed to take off and plunge fantasy movies back into the B-film ghetto. The story structure, where there is sort of an Level 1 Boss with Calibos, who then continues to plague the heroes as they contest against his mother (like Beowulf in structure with Grendel then Grendel's mother), works. Medusa is like a Level 2 Boss, and then an exhausting repeat of Calibos and then quickly to the Kraken as the final boss. (Thetis herself is never physically contested, just her scheme fails and she has to suck on that lemon).
This was Harryhausen's swan song, and it was a good one. There are so many effects in this movie, from Calibos to the little mechanical owl to the giant scorpions, to Medusa and the Kraken. According to Wikipedia, some of the final second conflict with Calibos was removed, which sounds like Harryhausen might have already had done the work to do it, which would have been an awful shame to cut. I am surprised the movie only has a 66% on Rotten Tomatoes (which still soars above the 2010 remake's score).