Ok, so in the first Fionna and cake episode, it focused on Prince Gumball and his relation with fionna and cake, also on that episode, we see a cameo of marshal lee, then the next episode we see marshal and his relationship with fionna and cake, and then we see a cameo of Lsp, now the latest episode has lsp and has a cameo of flame prince, sssoooooo the next ep probably has flame prince!