Downtown is one of the best and funniest shows ever. Notice here, I did not say "funniest animated show." I've wasted a pretty fair chunk of my life watching TV, and this is the cream of the crop, effortlessly. The style is still unique, after over a decade. There's something special about the jokes, like they contain a chewy nougat center of pure fucking Zen, urban satori at every turn. But that's not to say its so deep that it's suffocating. It's hard to really pin down what makes it so great. You have real characterization, realistic but amusing plots that hit close to home, and so much cool that aliens will find it in a time capsule someday and reinvent mirrored sunglasses.
Note: One reason for its "realism" is the fact that the show was based on interviews with real people. Some of this might be based on true stories.
It ran from August 3, 1999 to November 8, 1999 on MTV and was nominated for an Emmy in 2000 for best animated program, according to Wikipedia. It takes place in New York, New York, in roughly the same time as it aired.
Alex
A typical nerdy loser. Can't talk to most girls, socially awkward, hoards action figures, stuck at a crappy dead-end job that he's grossly overqualified for. His sister rags on him for being a virgin.
Jen
Alex's best friend. She usually cracks jokes and hates on everyone. Most people mistake her for being his girlfriend.
Chakka
She couldn't be further from my type. Everything about her is obnoxious: the sound effects, the gestures, the attitude, the drunken party chick chic, the trendiness... And yet, you can't help caring what happens to her. That is character development right there. Taking an extremely hate-able stereotype, and then adding enough humanity to make people like her.
Mecca
Chakka's best friend. Has lots of romantic day dreams. Kind of boring.
Fruity
As if to make up for his nickname, he hits on girls relentlessly everywhere he goes. They usually go for his friend Matt instead, but they pretty much always ignore him.
Matt
A street artist. He has that quiet cool; totally smooth.
Goat
Fans of Megas XLR may recognize him, and he's exactly the same character, only uncensored. Goat is awesome and crazy and hilarious. He represents the trashiest, sleaziest dude you know. Fun fact: he appears in an episode of Metalocalypse, where he gets killed or maimed. I think it was the Duncan Hills Coffee episode.
Jen's Roommate (Leah)
Really hot gold digger. Jen hates her sluttiness while envying her fun.
Alex's nerd friends
There's an Asian guy that usually tries to teach Alex the horrible futility of life. It's cold and unforgiving, he says. Not like those postcards or sitcoms or whatever. There's also a fat guy and an ugly guy. The ugly guy is sort of their liaison to the rest of the world. I think he looks a little like Byers from the X-Files.
Serene
Alex's big crush. A goth and a model and basically a person way to cool for him. He makes a good first impression with her when a bout of insomnia leaves him a tripped-out philosopher. He manages to impress her a few other ways, but SPOILER:
They're only ever friends.
So, where should you start with this show? I recommend Insomnia, Graffiti, Testing, and Hotel Bar. You'll end up watching them all, but those are probably the best. Your choices as of now are a torrent (I'll leave you to that one) or if you want to really own it, here and here.