Aviva is a member and the unofficial leader of the Wild Kratts crew. She is an engineer, and is the creator of all the Wild Kratts inventions, including the Tortuga and the Creature Power Suits. Athough many fan's show distaste towards what seems like Aviva yelling at the Kratt brothers, Aviva and Koki are portrayed as more mature-guiding sister figures for the brothers. In addition, she often is the one to get Martin and Chris out of sticky situations.
Kate Corcovado was once Zach and McKenzie Varmitech's daughter. But once the Wild Kratts got into her head at the age of four, she led her own path and became a Wild Kratt, thus betraying her father, Zach. For years, (and years to come) Zach and tried and tried to get Kate to come back to him, but he always usually fails, even when he tries by force.