2. Lucy and Ethel, 'I Love Lucy'
A great comedy duo is like a well-oiled machine, even when the machine is spinning out of control. So look no further for evidence of Lucille Ball and Vivian Vance's factory-precision teamwork than the legendary I Love Lucy episode where they become workers on chocolate-factory assembly line, keeping the candy moving by any means necessary. That was the secret to Lucy and Ethel's relationship: No matter what hijinks they got into, they truly felt like friends who'd do whatever it took to get each other out of it again.