Running Gags

The running gags in The Big Bang Theory include many stunts and dialogues that repeatedly come up in the episodes.

Stunts
Leonard
 * Getting mocked for his  and being short.

Sheldon
 * His inability to understand.
 * Sheldon's spot on the couch.
 * Sheldon's knock, knocking 3 times, saying the name of the person addressed, and repeating it twice after.
 * His blaming others for things that he has done.
 * His psychotic rants.
 * Someone asks Sheldon "Why?" and others get upset since Sheldon has been given an opening to deliver a long explanation.
 * Someone sings "Soft Kitty" to comfort Sheldon when he is sick, or vice versa.
 * Sheldon getting restraining orders.
 * Embarrassing Amy.
 * His constant asking questions about the food he's being served. Most of the time, Leonard gets it wrong with by one detail.

Penny
 * She gets promiscuous and morally loose when she drinks.
 * Her anger.
 * The "check engine" light in her car.
 * Her lack of education and awareness of not graduating community college.
 * Her sloppiness.

Howard
 * He gets mocked for without a, especially by Sheldon.
 * His sleaziness.

Raj
 * His, until the end of the episode "The Bon Voyage Reaction":
 * Being forced to whisper things, most often to Howard's ear, when he's near a woman (usually Penny).
 * He gets drunk to overcome his selective mutism but ends up saying very inappropriate things.

Amy
 * Monkey references and comparisons.
 * Girl crush on Penny.
 * Romantic frustration with Sheldon.

Bernadette
 * Her short temper and aggressive nature.
 * Her competitive side.
 * She sounding exactly like Howard's mother when she yells or gets angry.
 * She is constantly made fun of for her height.

Mrs. Wolowitz
 * She always yells from off-screen.

Leonard and Sheldon
 * Sheldon taunting Leonard with "The Roommate Agreement".

Howard and Raj
 * They seem as though they are a homosexual couple, but aren't.

Leonard, Penny and Sheldon
 * Leonard and Penny acting like Sheldon's parents.
 * Sheldon blaming Leonard for first speaking to Penny when she moved in the building in the pilot episode.

The stairs
 * Awkward silence while walking up the stairs.
 * Running down the stairs.

Others
 * Shot of a front door while a character abruptly exits with someone screaming "Get out!"

Dialogs

 * "Bazinga!" - Sheldon
 * "Once again, you’ve fallen for one of my classic pranks. Bazinga!" - Sheldon
 * "Here we go..." - Multiple users (usually followed by one of Sheldon's "psychotic rants")
 * "Holy crap on a cracker!" - Penny
 * "Whaaaaaaaaaaat?!" - Leonard
 * "HOWARD" - Mrs. Wolowitz
 * "I'm not crazy/insane. My mother had me tested." - Sheldon
 * "In what universe..." - Multiple users
 * "...jibber jabber..." - Multiple users
 * "...offer them a hot beverage." - Sheldon
 * "Oh not this again." - Sheldon
 * "Oh balls!" - Penny
 * "Oh (my) God!" - Penny
 * "...on purpose." - Multiple users
 * "Sweetie..." - Penny
 * "That's the spirit" - Leonard
 * "There, there." - Multiple users
 * "This may be the wine (magic potion) talking..." - Multiple users
 * "What the frak?" - Howard
 * "You're in my spot." - Sheldon
 * "You're welcome." - Multiple users (said before he thinks someone should say "Thank you".)
 * "Your check engine light is on" - Sheldon/Amy/Beverly
 * "...rat bastard..." - Penny/Amy
 * "...hippie-dippy..." - Sheldon