I used to find these LPs in thrift shops all the time... they were from the 1950s and early 1960s.
Along with the LP came a script. A star (Tallulah Bankhead, Cesar Romero, Vincent Price) would read half of the script, leaving appropriate pauses for you to "act" a scene with him or her. The best one was Arlene Dahl, because she was striking a sultry pose on a real leopard rug on the cover.
I imagine listening to "Co-Star!" would have been a pretty good guide to pencil-dialing ability back in the day.
Does anyone remember these?