Yesterday, the 'Toxic' hitmaker confirmed on Twitter that she was shooting her first scenes for her tribute episode.
Britney, who attached a picture for her fans, said: "About to do my first shot of the day for Glee tweeties! Here we goooo!"
Glee's creator Ryan Murphy recently confirmed that Spears would be guest starring, despite the fact that Jane Lynch - who plays Sue Sylvester - refuted the initial rumours.
> Glee Murphy: 'Spears will play herself'