Twilight - both a series of vampire-themed films, and the first of that series (to be followed by New Moon, Eclipse, and the two-part Breaking Dawn). Mark Kermode is a fan of all of them, although New Moon lets the side down a bit as Bella does too much sulking.
The Twiglet epithet came from a listener called Amber, who wrote an email that began "as a teenage girl..." and was shocked that Mark had not noticed the blatant sexism within the film, nor the fact that Edward - were he not so dull - would make an interesting case study in abusive partners. Mark disagreed that Edward was abusive and pointed out that the book was in the tradition of Gothic angst, which has long been pioneered by female authors - though he did concede that the words "as a teenage girl" were the trump card in any discussion on Twiglet. Simon Mayo, however, added that when he had mentioned the content of Amber's email to his own teenage daughter that morning, she had replied: "She's so got no friends."
Later, David Slade's being director of Eclipse meant that Mark could talk about Hard Candy - the leg-crossing date movie that he really loves.