From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Hei appeared in Dragon Ball Z: Bio Broly. He had the ability to shift between a normal, docile appearance and a monstrous form with red Cat-like eyes and razor-sharp claws and fangs. He growled at the Biowarriors when they were first released from their tanks. In a humorous scene, Jaga was shown to be small enough to ride on his back. He later snuck up on Son Goten and Trunks Brief as they spied on Mister Satan and the others and revealed his monstrous form. Although Trunks was intimidated by the sight, Goten easily tamed him and he took a liking to Goten. This led Trunks to remark "You have got to show me how you do that."