In "Glee's" second season, Brittany S. Pierce (Heather Morris) finally gets to meet Britney Spears, the bane of her existence, even if only in her imagination.

Inspired by Britney's own suggestion, the episode "Britney/Brittany" devotes nearly all of its musical numbers to Ms. Spears, with Britney making a few cameos in Ms. Pierce's anesthesia-induced fantasy sequences (courtesy of John "Have Mercy" Stamos as Hot Dentist Carl).

https://ew.com/tv/britney-spears-best-tv-performances/