Diamond Kings: A subset in Donruss baseball sets 1982-1991, featuring bad artwork of star players by Hall of Fame artist Dick Perez. Some people liked them though, and in the days of only three brands, a lot of people would collect just those cards as a topical subset. In 1992, Donruss changed them to inserts by setting them apart from the regular set. Their popularity increased further in 1996, when Donruss made them a serial numbered insert as "completists" wanted to keep their set runs alive.
Playoff revived the Diamond Kings as an insert in 2001, and issued a stand-alone DK product in 2002.