Murphy previously described the episode as "so reverential, so kind about her music."
Zap2it.com also reports that stage and screen vet John Stamos, who is set for a recurring role on the Fox series' second season as a dentist rival of Will Schuster (for Emma's affections), will have a role in the episode as well. Seems Mr. Schuster (Tony nominee Matthew Morrison) is against the glee kids singing Spears' songs, so when they visit Stamos in the dentist's office and go under the ether, they'll get to hallucinate the musical numbers. Spears will make her appearance in one of these dream sequences.
Here are the pics Spears tweeted: