It's rumored that Martin Abrams got the idea for the toyline after going to a marathon of Ape films with his son, the resulting sales of Mego Apes merchandise in 1974 reached $16 million.
Mego outbid rival AHI for the Apes License, it was a wise choice, in 1975 Mego's Planet of the Apes line was listed in the top five best selling lines of the year
Noticeably absent from the line is a Taylor doll, Neal Kublan explains why there was no Chuck Heston doll "Because we would have had to pay (Heston), he had that kind of a contract, so we just used a character; the helmet comes from Action Jackson, the jumpsuit too. We never made a new tool if we didn't have to."
The Astronaut head is an early figure used in test shots as Dinah Mite's boyfriend Don (Superman later took that role).
Note the prototype cards in these shots