The Clasico rivalry is so intense that it is considered taboo to represent both Real Madrid and Barcelona during a player's career. The two old rivals meet once again on Wednesday in the Copa del Rey - and no one in the current crop on either side has been brave enough to cross the divide.
However, there is a long list of brave souls who have dared to turn their backs on one of the Spanish giants and end up sporting the jersey of the other.
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Youngster Iker Bravo is the latest to do so. Once a bright prospect in Barcelona's La Masia academy, he has ended up at Real Madrid on loan via Bayer Leverkusen just one year after contract extension negotiations broke down with Camp Nou club.
Is it possible for him to succeed at the Santiago Bernabeu despite his history? GOAL takes a look at the long list of stars who have been part of both organisations before him...