Buffy the Vampire Slayer

 was a television series. By 2600, it was in its 792nd season. (PROSE: The Glass Prison)

Slake referred to Samantha Jones as "Buffy the Vampire Slayer" after she killed Weird Harold. (PROSE: Vampire Science)

Rose Tyler, while fighting a Mantodean, thought to herself, "Forget Buffy, this was Rose the Giant-Insect Slayer." (PROSE: Winner Takes All)

In the Main Hall of Geath, Rory referenced their adventure in Venice (TV: Vampires in Venice) when he said, "Fight the odd vampire..." to which the Eleventh Doctor replied, "Technically, they weren't vampires. Do I look like Buffy?" (PROSE: The King's Dragon)

Behind the scenes
In the short storyHomework, a character from the year 2008 is said to be wearing "a T-shirt that said Duffy the Vampire or something," most likely a reference to the series.