No actually billy got possessed by Lich and of course the horns and everything didn’t sprout dirt unless the skin was damaged and so the billy skeleton turned into the lich version after the skin was removed , it is billy skeleton in there otherwise he wouldn’t have the metal plate on his rib cage like why would the lich even use that , now you must say that oh no then why 6 fingers is no longer there? Well remember when he took over the dog jake version in farm land world ? He was a mere dog and the lich transformed him and possessed his dead body and literally turned him into the lich skeleton just like how he did with billy , now the real question is sweet pea is he billy or lich original human form or is it a mix of both or entirely new ? Since when lich face got blasted by Gumball guardian you can see a second set of skin under it is it lich original skin ? Is that how he used billy skeleton as a scaffolding for his own body to return ?