Upon his return, Golan was horrified to find the residents of Gkruool were now happier than ever. Celebrating Golan's absence, dancing merrily and even passing out T-shirts that said "Golan Sucks" on them. Upon discovering Golan had returned, his own subjects chased him away. Golan now plans to return one day and retake his kingdom from Kruung and his former followers.
The concept of "Gkruool" is exactly as old as Golan himself is. The concept of Golan's world was mentioned in the very first published story Golan appeared in. In the first iteration of Golan's continuity, it was not explained how Golan ended up in our dimension. Golan himself said he wasn't sure how, but suspected "foul wizardry."
This backstory was carried over into the first season of the show, where Golan and Dylan were totally unaware how he ended up on earth. Dylan would often tell Golan how badly she wanted to come to Gkruool with him one day, but Golan seemed adverse to the idea.
In the second season, it was finally explained how Golan was separated from Gkruool. Dylan found a demonic tome in the basement of her mother's work and summoned Golan with a magic spell. Golan was able to return to his dimension, but was rejected by his own people.