SlidellMan

The '74 Mad Magazine TV Special and Cartoon Network's MAD also had them. By the way, the '74 version was in color.

Here's the Mountain Dew ad:

I'm still baffled that they never adapted any of the strips with the Gray Spy aka the Woman Spy.

I was always more into Cracked than Mad growing up, but Spy vs. Spy was awesome - both as a comic and a c64 game!