Jason

 is a dark yellow hippo and the older brother of Tasha.

has almost the exact opposite personality of Tasha. While Tasha can be a little bossy depending on which character she plays, Jason has a very pleasant side. Sometimes he would discipline his sister for her behavior, because he's older than her, but he only does that when they make-believe. Also, when they make-believe, they would tend to bicker with each other.