Final answer:
Will Schuester finds a compromising tape of Sue Sylvester singing and dancing in the first season episode 'The Rhodes Not Taken' of Glee.
Step-by-step explanation:
In the first season of Glee, the character Will Schuester finds a compromising tape of Sue Sylvester singing and dancing. In this episode titled 'The Rhodes Not Taken', Will Schuester discovers the video while going through some old tapes. The video is of Sue Sylvester, the coach of the cheerleading squad, performing a heartfelt rendition of 'Physical' by Olivia Newton-John. This tape becomes a major plot point in the episode and leads to some interesting developments in the storyline.