Launching in 1987, Cassie was a line of 11.5″ fashion dolls from Select, similar to Hasbro’s Jem and the Holograms, and Mattel’s Barbie and the Rockers. Cassie came with a display stand and a karaoke microphone that allowed for anyone to sing along with Cassie by utilizing the 3.5mm headphone jack in the base. 

Check out the fan site Totally Jem for more information.