Into musical theatre

Tallulah speculated that the Tenth Doctor was not interested sexually in his companion Martha Jones because he was "into musical theatre". Once the implication of the statement registered on Martha, she was quick to try to correct the actress, but she never was able to fully disabuse Tallulah of the notion that the Doctor was "waste[d]" on women. (TV: Daleks in Manhattan)

Behind the scenes
The clear implication of the phrase was that the Doctor was gay — though Tallulah never said so directly.