The toy worked by using a simple molding process. One- or two-sided molds were filled with a supplied plastic goop which were then heated; the goop would firm up and and the result would be a small rubbery item such as a bug or even a miniature plastic toy soldier. In the case of Vac-U-Form and Vac-U-Maker, children would work a small pump to force the plastic to extrude within (or around) a certain shape.
Because of the heating element (and the perceived toxicity of the goop), the toy was subject to much parental and alarmist scrutiny, and as a result, disappeared for some time. It is again available for modern children, however, thanks to companies other than Mattel; and with the right supervision, it is as safe as any other complicated plaything.
The most popular Thingmaker spinoff sets included:
Vac-U-Form and Vac-U-Maker - the original toys which actually preceded Thingmaker. Beginning with Vac-U-Maker, kids could make their own little plastic versions of bugs, lizards, toads, and spiders.
Creepy Crawlers - the original toy to fall under the category line of 'Thingmaker.' It contained molds for a surprisingly large variety of creatures, and even included small clear-plastic wings to attach to the flying insects. An offshoot of this was the Giant Creepy Crawlers set, which featured larger insects, one to a mold (whereas the previous set's molds allowed the creation of two smaller creepies at once).
Fright Factory - a delightfully fiendish set which allowed kids to create 'scary' items like little skeletons, shrunken heads, and even vampire teeth to wear to the dentist's office.
Creeple Peeple - a set for producing weird little creatures (like something out of a Basil Wolverton nightmare), complete with arms and legs, that one could stick on a pencil to make little figures.
Fun Flowers - this being the 1960's, kids could make their own little plastic flowers in a variety of designs and colors.
Fighting Men - for producing little plastic toy soldiers. Actually one of the more innovative sets, this one allowed to kids to also create little weapons and accessories for their very GI Joe-like little warriors.
Super Cartoon Maker - this set allowed kids to make their own little comic strips; molds were provided to create miniature Peanuts characters such as Snoopy and Linus, and kids would place the plastic figures over a printed comic-like background.