Because you like Bobby Wheeler in Taxi
Although Penny's friends have genius-level IQs, they regularly come to her for advice and insight. See them in The Big Bang Theory.
Whether it's randomly bursting into song or writing Nancy Drew fan-fiction, Jess proudly marches to the beat of her own drum. See them in New Girl.
A fourth grader without a moral compass, Eric Cartman lives on KFC, Taco Bell, Pizza Hut, and Cheesy Poofs. See them in South Park.
Bedside manner is for chumps, not the brilliant Dr. Gregory House. See them in House M.D..
Korra is stubborn, outgoing, and faced with huge responsibilities she might not be ready for. See them in The Legend of Korra.
Tina Belcher is on the cusp of puberty, and she has no shame when it comes to boys, butts, and brassieres. See them in Bob's Burgers.
Joey Tribbiani's true passions in life are acting, sandwiches, football, sex, and asking ladies, "how you doing?" See them in Friends.
Sheldon Cooper is brilliant in every way except, well, interacting with any human being. See them in The Big Bang Theory.