In the NYTW version of Rent from 1994, Mark was much more upset about Maureen than he is in the version that made it to Broadway. He and Maureen are a much bigger part of the show.
In that version of I'll Cover You:
Mark sees Maureen and freaks out, and later in Christmas Bells:
he tries to tell Roger about it but Roger's a little distracted. They have this exchange
ROGER: No kisses...
MARK: I saw Maureen!
ROGER: No alcohol...
MARK: She's in the lot!
ROGER: No sex!
MARK: She still might care!
ROGER: Look! That's her there!
ROGER: There! That's her!
Neither of them is listening to each other so when Roger goes "There! That's her!" Mark assumes he's been listening to him and thinks he sees Maureen. It just didn't get cut.
Mark and Maureen also have a song in NYTW that was the predecessor to Tango: Maureen. It's called You'll Get Over It and is absolutely hysterical.
Sorry it's a little long, but I get really excited talking about Rent.