This is an interesting start!  Two comments:  one, I find that the name before the talking heads, i.e. "Jim." before his talking head in italics is distracting.  The fact that you put the talking head in italics helps distinguish it for what it is and makes the name-bit unnecessary.  

Two:  are you really going to make Missie a possible love-interest for Jim?  I mean, I guess if they were exes, it's always possible, but if Missie knows that Jim's always had a thing for Pam and then she gets in-between them, wouldn't she kind of feel like an asshole?  Something to think about as you continue it.

Also:  I'm kind of interested in Karen's reaction to having Missie in the office.  I like the fact that Pam acknowledges that they might be friends (poor Pam needs a friend) -- but how does Karen react?  Does she know who Missie is?  Did Jim and Karen talk about her ever?  Is she going to be threatened by her?  I'm curious about this dynamic.  I don't think you need to make Karen "catty," per se, but I think she'd be a little cautiously suspicious.  Karen always seemed like the type of person who had more guy friends than girl friends (and Jim, I think, had a good combination of guy and girl friends).  If I were Karen, I'd be a little exasperated at having another Jim Halpert friend/love interest in the office. 

Anyway, definitely interested to see where this goes.