I used to see the commercials every time my sister watched Nicktoons when I was about 2 or 3 and the most iconic I remember was when Errol was on a bike by the moon and he said "Add milk or we'll crusha!". There was also one where he was parachuting and the cows got squished. They also were sponsoring afternoons on Nickelodeon. I actually used to get hysterical at the jungle one where the cats got thrown off the vine and the scream that starts the ad before Errol says his catchphrase.
I think they aired during the SKC and S&L era. They don't air anymore but they used to air the ones where Errol and the kittens were on flying milk bottles.