Mr. Treeger

Mr. Treeger is the superintendent of Monica's building. Treeger first appears in "The One Where Heckles Dies", where he shows Heckles's lawyer where Monica and Rachel live. He next appears in "The One with Phoebe's Dad", where Monica thinks he is playing hardball by not mending her broken radiator. In "The One with the Ballroom Dancing", he threatens to have Monica and Rachel evicted unless Joey helps him practice ballroom dancing to impress a woman. In "The One with the Free Porn", he cleans the shower drain of Chandler and Joey's newly-won apartment, and warns them never to turn off their TV after they start receiving free porn. In his final appearance in "The One Where Rachel Tells Ross", he has a fireman break down the door to Monica's apartment after Joey tells him he smelled gas.
Mr.Treeger's homour is kind of ironic and humiliating:

[Scene: Garbage room: Mr. Treeger is unclogging the trash chute as Rachel enters.]
RACHEL: Oh! Hey, Mr. Treeger.
MR.TREEGER: Hey.
(Rachel opens the trash chute, winces at the smell, and throws the garbage bag in. She then tries to throw the pizza box in, but since it’s so big she jams it into the opening and it prevents the door from closing. She then turns around too see Mr. Treeger watching her.)
MR.TREEGER: What are you doing?
RACHEL: Ummm. Oh! I’m sorry. (She grabs the box and offers him a piece.) It’s a little old but…
MR.TREEGER: No! You’re clogging up the chute that I spent a half-hour unclogging!
RACHEL: I’m sorry. I didn’t...I don’t come in here a lot.
MR.TREEGER: Oh yeah, of course you don’t!
RACHEL: No.
MR.TREEGER: ‘Cause you’re a little princess! "Daddy, buy me a pizza. Daddy, buy me a candy factory. Daddy, make the cast of Cats sing Happy Birthday to me…"