While Glenn was a prince, he fell in love with a witch, Joanna while on vacation in uptown New York City, and the two planned to elope together. Before they could do so, he was turned into a frog. He believed that this was because Joanna's coven didn't approve of their relationship. However, he later found out that he had been turned into a frog by Joanna as part of her midterm exams (her final exam was to change him back).
Glenn first met the Doyles while they were vacationing in their country home, where they helped two of his friends work through their relationship difficulties. He believed the Doyles' dedication to the cause of true love would motivate them to help him and his similarly-cursed brother, John. The Doyles went with him to visit the Joanna and were eventually able to help him return to a human state.
He thinks lilypads are overrated.