(written from a Production point of view)
Mego Toys (pronounced MEE-go) was a prime producer of licensed action figures in the 1970s and early 1980s. Besides producing the first Star Trek action figures and the figures for Star Trek: The Motion Picture, Mego was also responsible for the infamous World's Greatest Super Heroes (WGSH) line of DC and Marvel Hero figures, as well as figures for Space: 1999, Planet of the Apes and many other genre projects.
The company began in 1954 producing standard dolls and other toys. Beginning in 1971, they began producing the first 8" action figure, called Action Jackson. The figure was meant to compete with Hasbro's well-established G.I. Joe line. They began production of the WGSH figures in 1972. By 1975, they started the line of Star Trek action figures and toys and starships, which continued until 1978. In 1980, they produced the Star Trek: The Motion Picture figures and toys. However, due to declining sales and the loss of their bid to produce the Star Wars toys to Kenner, Mego declared bankruptcy in 1982 and had closed their doors by 1983.