He is in love with Videl and sought to unmask the Great Saiyaman to impress her. It wasn't until Gohan's fight with Kibito that everyone learned that Gohan was the Great Saiyaman. When Sharpner learned of this, he cheered Gohan on to win the fight.
He was likely killed when Super Buu wiped out nearly all of Earth's population, but when he was revived thanks to the Namekian Dragon Balls, he gave his energy to Gohan's father, Goku to destroy Kid Buu. He was never seen in Dragon Ball GT, but he appeared briefly in Wrath of the Dragon telling Gohan he was late.