A contradiction concerning the idea of "multiverse", find the flaw
Two men are discussing the idea of a multiverse, and one of them suddenly jumps up in excitement.
"I can disprove the theory of the multiverse!" the man says.
"How?" asks the other person.
"Well, if there exists at least one universe for every possibility then there must be a universe where there isn't a multiverse! If there is a universe where there wasn't a multiverse then how was that universe created? It wasn't! Therefore it's a paradox!" he says confidently.
"Haha, nice try, but I know where your argument falls apart," responds the other guy, with a grin on his face.