Complex sentence: Casper believed that he is lonely and all he wanted was to be accepted, but Wendy and Hot Stuff thinks that he is crazy, which led into a huge argument between Casper and Wendy ending their friendship leaving Hot Stuff by himself.
Split into simpler sentences: Casper believed that he is lonely and all he wanted was to be accepted, but Wendy and Hot Stuff thinks that he has lost his mind. This lead Casper and Wendy into a huge arguement and ending their friendship leaving Hot Stuff by himself.