How can I be more funny and charismatic?

How can I be more funny and charismatic? I like to think I can do anything regardless of my stutter but often I feel like I'm not charismatic or funny. It's hard when people are having conversations and I'd like to chime in but the moment passes. It's even worse when someone says something funny while I was struggling to say it or right in the middle of saying it. So how can I work with my stutter and build up my charisma? I don't ever think I'll be like Obama but I'd like to try and work with the situation I've been given.