I used to wonder why Maxwell was so oblivious to C.C.'s obvious interest in him then it hit me, she's always been obsessed with him and likely has always acted this way. As far as he's concerned she's just acting normal and probably just thinks she's kidding around, especially since she would have acted like that while he was married.
Okay, so C.C. and Niles marry as Fran is delivering her children because C.C. felt strange since Niles proposed. And guess what? It turns out C.C. is pregnant! Sure, it sounds dandy now, but we learn this after Fran's water breaks in the elevator and we briefly see C.C. drinking from a small bottle typically used for alcohol.