Mattel was the “primary target” for MGM’s massive, and very successful, marketing campaign for Clash of the Titans. The film was panned by critics, but ended up the 11th highest grossing feature of 1981. Here’s a snippet from the Schenectady Gazette (August 30, 1980) describing the merchandising, apparently the “most extensive… ever accorded an MGM motion picture.” (There’s also an interesting December 1982 article here about the dangerous business of toy licensing: Mattel’s Clash line is noted as one of the “bargain-basement items.”)
Mattel’s effort on the toys was less than impressive. A second wave may have been planned, but too many major characters were left out initially, and only two creatures were produced (Pegasus and the Kraken—neither was convincing) for what was essentially a creature feature. How did we not get Medusa, who represents the climactic moment of the movie and is arguably Harryhausen‘s magnum opus?
Having said that, whoever designed the packaging belongs in the toy hall of fame. I can still remember those cards hanging on the hooks in toy stores. The unforgettable look did not go unnoticed by Hasbro, whose G.I. Joe: A Real American Hero packages would fashion the bold mix of deep red, orange, and yellow into an explosion surrounding each figure and vehicle.
I’m adding some price tags below, from highest found to lowest found. 25¢ apiece on clearance! The rest of the Clash toys are here.
2 Warps to Neptune 
Yeah, the packaging really outclasses the toys although they’re not *that* bad.
I never had any of them but I remember really wanting Charon and the strength of the packaging certainly helped capture my imagination and overlook the general meh-ness of the actual figure.
Plus I had a thing for cloaked skeletons.
I had all of the figures. Not sure when I got them, but it must have been when they were way reduced. I loved the movie and was getting into D&D at the time. So funny that Charon was a figure. He/it is in the movie for only a minute. We were all suckers for skeletons!
I had Calibos: his tail snapped off instantly, and I don’t know how since I was never rough with my toys. Love that card art, though!
I had them too.