Live4MusiC

Writing on Twitter as the show screened on the U.S. west coast, Spears said: "I loved it! Thank you guys SO much for making this happen!"

Last season's Madonna-themed episode was a ratings success, while buzz has been circulating for weeks around Tuesday's "Britney/Brittany" episode.

The episode opened with teacher Will Schuester, played by Matthew Morrison, trying to prevent his singing group from channeling the sexy pop icon, instead encouraging them to sing adult contemporary music at a McKinley High School Homecoming assembly.

Despite Morrison's attempts, New Directions take to the stage with a sexy cabaret-style of Toxic with Morrison himself joining in.

Spears made two appearances on the show when glee club members envision the pop legend during anesthesia-induced dreams during visits to the local dentist -- a role filled by John Stamos.

"You're really hot ... and your breath smells really good," ditzy cheerleader Brittany (Heather Morris) said when she came face-to-face with the real-life Spears in a dream.

Morris paid tribute to Spears' 2001 MTV Video Music Awards performance of I'm a Slave 4 U complete with a live snake, resulting in the singer tweeting: "I know how hard it is to dance with that snake! Nice job...."

The show's creator Ryan Murphy said the episode was designed to show off the skills of Morris -- a former backup dancer for Beyonce Knowles.

Murphy told Entertainment Weekly that he next wants to tackle the songs of Bruce Springsteen or Michael Jackson, while an episode based on the musical The Rocky Horror Picture Show is in the works.