Transformers: Animated - Season 1 Episode 10 -

Megatron creates Soundwave, a robot in the form of a toy robot for Isaac to give to Sari for her birthday. Bulkhead is the only one who finds the toy to be a bad thing and finds out that the toy is evil. Unknown to Sari, the more she uses her key on Soundwave, the more he will evolve into a bigger robot.