The line "Judoon platoon upon the Moon." was written as something of a joke towards David Tennant. The Scottish accent, which is Tennant's natural one, makes it difficult to pronounce the sound/syllable "-oon" in an English accent.
When Martha and The Doctor first step out onto the balcony and Martha says that the cause must be extra-terrestrial, she refers to a cousin, named Adeola. Freema Agyeman played the character Adeola in Army of Ghosts (2006). It was this role that convinced the directors to choose her to play Martha.
The Doctor for the first time reveals that he has (or, rather, had) a brother.
When the Judoon are first cataloging all the patients, The Doctor mentions that the hospital has a shop. In New Earth (2006), The Doctor expresses his disappointment that there isn't a shop in the hospital with Rose.