Sadly she got replaced by Kate Hodge when the show changed to Love And Curses
Part of the first wave of Animorphs toys, Cassie transforms from what is evidently supposed to be a human into a wolf, as well as a transitional third mode combining features from both. Like many Animorphs toys, she has a pair of wolf claws that attach to her hands like gloves; unlike the other toys, they are not actually necessary to complete her wolf mode (as it has four paws already), though they can still be used in that mode.
Tri-Rex (Super, 1999)
This version of Cassie was available only in the Tri-Rex giftset, along with Jake and Marco. The toy has neither a human mode nor a complete animal mode; Cassie transforms from a human/dinosaur transitional form into the tail of Tri-Rex.
Notes
Cassie holds the dubious honor of having perhaps the least informative bio note ever. It mentions her wolf mode, but beyond that it simply reiterates the Animorphs premise, with no information whatsoever that specifically pertains to Cassie herself.
