[1] X Sporting Club is best remembered for its role in the founding of RCD Espanyol in 1909.

[2] Established in March 1902 under the name of Football Club X, and in 1903 it occupied the football field of the newly defunct Irish FC at the Nuevo Velódromo de Barcelona in Carrer Aragó.

In 1906 Club Español de Football (now RCD Espanyol) had to suspend its activities due to a lack of players, since most of them were university students who enrolled to study at universities outside Catalonia.

[2] Some victories were controversial, especially the last season, where the Catalan Federation, led by X director Isidre Lloret, was accused of favoritism towards his team.

This period, from 1906 to 1909, when Español ceased its activities, is now considered an "impasse"[a], and "The Incognitos", as the team was known, was nothing but a continuation.