Just a note-- The piece mentions the Derby-BC Classic doubles of Ferdinand, Alysheba, Sunday Silence and Unbridled in 1987-1990.

It's worth noting that in 1987, 1986 Derby winner Ferdinand came back as a 4 year old to beat that year's winner Alysheba. Alysheba came back in 88 as a four-year old to give the Classic a second go (and win). So Ferd and Alysheba aren't really examples of the Derby-Classic double (done in the same year), but rather examples of longer racing careers.

(It's also interesting to note that those two great champions have had questionable--and tragic--careers at stud. Ferdinand wound up in Japan, where he was sent to a slaughterhouse at age 19 when his offspring proved disappointing. Alysheba is at stud in Saudi Arabia, though many are trying to bring him back to the US for retirement.)