Original 1976 "Slime" (Mattel) smelled horrible, but, everyone had it. Gross thinking how most of the class shared the same kid's slime (who ever was spoiled/wealthy enough to have the lastest toys). "Hey can I play with your slime after math?
A kid could get lost in the story the viewfinder slides tell. There were no sounds but I often could picture how it was and how it would feel like going with my favorite cartoons on an adventure. The Viewmaster