These 2 vinyl puppets were named: Wilkins and Wontkins.
The ads starred the cheerful Wilkins, who liked Wilkins Coffee, and the grumpy Wontkins, who hated it. Wilkins would often do serious harm to Wontkins in the ads—blowing him up, stabbing him with a knife, and smashing him with a club, among many other violent acts.
Wilkins and Wontkins were generally the only characters in the commercials, though on rare occasions, such critters as a Muppet whale or baby birds would appear. Company owner Mr. Wilkins was also invoked more than once.
The characters proved so popular that in June 1958, the company offered vinyl puppets of Wilkins and Wontkins through the mail for $1.00 and a coffee can label. The offer on the can said, "Hey Kids! I'm Wilkins—he's Wontkins—you see us on TV!" Obviously, Wilkins Coffee and Henson knew that the Muppet characters had kid appeal, although this doesn't seem to have had any effect on the use of violence and terror in the ads.
The only time Wontkins was caught drinking a coffee that was not Wilkins was in the 1958 "Steamroller" ad.