Why?
I love them all but I always do this when I watch a show. Which one could this show lose (for a number of reasons, like an actor wants out but theydecide to keep the show going) and still be as funny and fun to watch,.
Penny is the only one

Like Friends when R&R had to stay away from each other becasue of Emily and Rach said Pheobe doesn't live close, she isn't related to anyone she could easily be lifted out