The old Underdog cartoon show from the 60s, made by the same guys who did Tennessee Tuxedo and Rocky & Bullwinkle. They'd have one Underdog short at the beginning and one at the end of the program, then they'd have another cartoon or two in the middle (like Go-Go Gophers and Klondike Kat and Commander McBragg).
There was one of those cartoons revolving around a character known as The Challenger. If I remember correctly, his alter ego was a cabbie who drove around in his Taxi Cab which became his supervehicle when he became The Challenger, a Green Hornet-ish pretend-bad-guy-who-was-actually-a-good-g
Does anybody have or can point me to a picture of this? Want to make an icon, and my Google-fu isn't working, partially because Underdog and Challenger are used every day in reports involving boxing, but I wonder if I've just plain hit something too obscure for even Teh Internet.