You can spawn a 25-year-old version of any living celebrity, once. Who are you picking?

It will be this person exactly as they were on their 25th birthday. You want Eminem? He pops into existence exactly as he was on October 17th, 1997.

They don't go away after either, they are their own person with free will. It has to be a real celebrity. I'm not going to define celebrity for you, just someone who is recognizable to a huge amount of people.