Horse Racing - allow horses to come back and defend their Derby titles... only being eligible once is dumb.
Like your initial post, but this idea sucks. You get one shot to win a Kentucky Derby. As a 3 year old. Period. That being said, champions can defend their Breeder's Cup titles. Several have repeated, including Mizdirection (Jim Rome's horse) and Wise Dan last year, and one horse (Goldikova) won 3 in a row.The following horses have won the same Breeders' Cup race at least twice:
Classic: Tiznow (2000, 2001)
Filly & Mare Turf: Ouija Board (2004, 2006)
Distaff: Bayakoa (1989, 1990), Royal Delta (2011, 2012) From 2008 to 2012, this race was known as the Ladies' Classic.
Mile: Miesque (1987, 1988), Lure (1992, 1993), Da Hoss (1996, 1998), Goldikova (2008, 2009, 2010), Wise Dan (2012, 2013)
Sprint: Midnight Lute (2007, 2008)
Turf: High Chaparral (2002, 2003), Conduit (2008, 2009)
Turf Sprint: Mizdirection (2012, 2013)
Filly & Mare Sprint: Groupie Doll (2012, 2013)
The following horse(s) have won two different Breeders' Cup races:
Zenyatta, Distaff in 2008, Classic in 2009.
Beholder, Juvenile Fillies in 2012, Distaff in 2013
Secret Circle, Juvenile Sprint in 2011, Sprint in 2013
The following horse(s) have won the same Breeders' Cup race three times:
Goldikova, Mile (2008, 2009, 2010).
The oldest horse to win a Breeders' Cup race is Calidiscopio, age 9, who won the Breeders' Cup Marathon in 2012.