I just ran across this old ad for Milky, the Marvelous Milking Cow on Reddit, and wow, it's a good reminder of how strange the 1970s were. You feed Milky water, pump her tail, squeeze her udders, and voila, a white "pretend milk" squirts out. The big question is, what was in that mysterious pretend milk, and was it edible?
The toy was released by Kenner in 1977, the same bizarre decade that brought us Baby Wet & Care (also Kenner), the doll that gets a rash on her bum after you feed her a bottle: