"William," Season 9 Episode 16

"William" is undoubtedly one of the most heartbreaking and divisive episodes of The X-Files due to how Scully decided to try and protect William for the rest of his life. It set the stage for the William status quo in both the I Want to Believe feature film and Season 10. The episode featured the unexpected return of a character presumed to be dead who will soon be back. Interestingly, it also featured the return of David Duchovny, although his contributions were behind the scenes as director. With Duchovny back on set, Gillian Anderson seemed more alive in "William" than all the previous episodes of Season 9, which is a testament to the chemistry that powered the show for so many years. Besides, even if you hate the William arc and/or how the episode ended, it's at least worth watching to admire how adorable he is.