Few things have an identification with the words "the seventies" and "toys" like Stretch Armstrong, the stretchable superhero was a phenomenon that had kids wondering "what's inside?"
By 1978, Kenner had expanded the line to add some new characters including the incredibly popular Stretch Monster
Stretch himself hadn't changed for 1978 but his box now had a window so you could see a figure inside. This seems like a bad idea, curious kids would just have to poke him or worse. I know this from experience, my mother mother told me there was corn syrup inside but I still ended up biting him ala dracula to see for myself.
Stretch Monster was the uber cool adversary for Stretch Armstrong, most 70's villains fell flat compared to the hero but Stretch Monster outshined his nemesis. Maybe it's the Sleestak vibe but Stretch Monster is the most desirable stretch figure Kenner ever produced.
Stretch Octopus was an attempt to get younger children and girls into the Stretch doll fold.
I love the expressions on the kid in the yellow.
Article about the launch of Stretch Monster from the 1977 Toyfair.
Boxed Stretch Monster doll (Courtesy of Count Balicki).
Stretch Armstrong lasted for another two years and would add another character (Stretch X Ray), the next year Mego would launch their own line of Stretch Super Heroes that would have Kenner seeing red.