the signs as sitcom archetypes
aries: The Bully-The domain of the Deadpan Snarker or the Pungeon Master. Despite the name, The Bully is oftentimes not an actual bully per se, but is usually aJerkass, or sometimes a Jerk with a Heart of Gold. Typically more outright beligerent than The Wisecracker, The Bully will have the least patience with The Wisecracker (who isn't afraid to stand up to him/her) or The Goofball (who is more often than not oblivious to the animosity); on the other hand, if written as a complete Jerkass, The Bully may actively dislike all the other characters. If female, this will be the Alpha Bitch or the Rich Bitch. In Work Coms, The Bully will be excessively driven to climb the corporate ladder and/or dominate the others, whether a Pointy-Haired Boss or a co-worker. [eg. Jackie Burkhart in That '70s Show.]
taurus: The Square-Often the central protagonist, and usually The Everyman or the Only Sane Man. Essentially the Straight Man; this doesn't mean necessarily that The Square gets no funny lines, but a large portion of the comedy from such a character comes from his/her reactions to the situation or other characters. In a Dom Com, this role will usually be reserved for the Closer to Earth mother figure. [eg. Eric Foreman in That '70s Show, Cory Matthews in Boy Meets World.]
gemini: The Bigmouth-A (sometimes) softer, less-hateful alternative to The Bully, The Bigmouth is an annoying, um, bigmouth. Whether s/he is a Know-Nothing Know-It-All; an overbearing egotist like the Small Name, Big Ego; or an intrusive Nosy Neighbor, The Bigmouth just has a knack for getting on everyone's nerves (with the possible inclusion of the audience!). Much much humor is milked from the fact that The Bigmouth isn't nearly as smart as s/he presumes to be. Oftentimes crosses over with The Dork. [eg. Pheobe and sometimes Ross in Friends, Ted Mosby in How I Met Your Mother.]
cancer: The Precocious AND The Goofball: see leo and pisces.
leo: The Goofball-This role is typically filled by The Ditz or the Cloudcuckoolander, but the character could also be generically zany or a Blithe Spirit rather than outright ditzy. Could also be a Pollyanna, with naivety serving as the defining trait; if so, expect this to be the youngest character (see also The Precocious) or a Naïve Newcomer. In Dom Coms this can be an air-headed child — typically a daughter— and a (sometimes) milder incarnation can take the form of a Bumbling Dad. [eg. Kelso in That '70s Show.]
virgo: The Stick-Crank The Square up to eleven, and you have The Stick. This character is extremely uptight and stuffy, a stickler for the rules if you will, a stick in the mud as it were. Usually humorless,often humorously so. Not unlike The Square, the humor from The Stick generally results from his/her dismay or outright horror at the antics of the others, and s/he may frequently insist (usually to no avail) that everyone should adhere to his/her mile-high standards. Oftentimes The Stick can overlap with The Bully, or even The Dork. On those shows wherein The Stick co-exists with The Square, The Square is more likely to be the central character. [eg. Monica in Friends, Lily in How I Met Your Mother.]
libra: The Charmer-This character comes in two varieties: First, The Casanova, the lover, the player. Enough said. Second, a more classically refined character, someone who is a devout adherent to old-fashioned politeness, grace and decorum (but not nearly so uptight or demanding of others as The Stick). [eg. Barney in How I Met Your Mother, Joey Tribbiani in Friends.]
scorpio: The Wisecracker AND The Dork: see sagittarius and capricorn.
sagittarius: The Wisecracker-This character just lives to make fun of others (not usually mean-spirited, like The Bully) or to find the humor in any given situation. Is usually something of a thorn in the sides of the others, particularly in more serious situations. Expect this character to have an especially conflict-laden relationship with The Bully, though the two can be (and often are) good friends underneath. [eg. Chandler Bing in Friends.]
capricorn: The Dork-A Hollywood Nerd/Geek. The Dork need not be stereotypically nerdy or geeky, at least not visually, but should be such relative to the other characters. In a cast full of such characters, The Dork will be the most obviously "dorky" of them. In shows with no obvious Goofball, The Dork may fulfill that role as well. And if a show needs a Butt Monkey, who better than The Dork? [eg. Freddie in iCarly, J.D. in Scrubs.] aquarius: The Sage-Usually an older character, this person acts as a sort of Mentor to the main characters, dispensing advice and An Aesop or two. Though close to the main group, The Sage generally exists outside that group, for example a neighbor, or an authority figure such as a teacher. In Sit Coms of old this position was typically filled by a wise, calm-voiced father figure, but that character type has been largely supplanted by the Bumbling Dad. Indeed, The Sage himself is becoming a forgotten character type these days, as the main characters tend to share the Aesop-dispensing chores rather than get them from a singular source. [eg. Giles in Buffy the Vampire Slayer] pisces: The Precocious-The (usually) youngest, cutest member of the cast (this character really flourishes in Dom Coms), this sweet, adorable little angel's principal reason for existence is to make the audience go "awwwww.” Usually fulfills the Pollyanna, Kawaiiko orMoe role, but can get in a few sharp quips as well. Also, this kid's pure innocence can bust through the toughest Aesops imaginable. [eg. Michelle in Full House.] (source: http://tvtropes.org/pmwiki/pmwiki.php/Main/SitcomCharacterArchetypes)