Episode: "Eclipsed" (Season 2,Episode 13)
This one is so obvious that it's really hard to believe censors didn't notice it. In an exchange between The Flash and Hawkgirl, the former brags about how he's the fastest man alive, leading to a hilarious response from the latter: "Which might explain why you can't get a date." Yes, The Flash has got the speed, but what about the endurance and stamina? Hawkgirl seems to think he's lacking in those departments.