The Wild Thornberrys

You Ain't Seen Nothin', Yeti (2x11)

Air date: Sep 01, 1999

To study and protect the snow leopards from extinction and a construction site that is threatening their survival, Nigel's mentor (thought to be lost for many years) has left civilization to be a yeti. Eliza discovers his identity, helps him fend off the construction workers, and reunites him with her father.