"William" is the sixteenth episode of the ninth season of the American science fiction television series The X-Files, which originally aired on the Fox network on April 28, 2002.

The show centers on FBI special agents who work on cases linked to the paranormal, called X-Files; this season focuses on the investigations of John Doggett (Robert Patrick), Monica Reyes (Annabeth Gish), and Dana Scully (Gillian Anderson).

In this episode, Doggett finds a strange, disfigured man (Chris Owens) in the X-Files office and, on his whim, they test his DNA.

"William" marked the return of David Duchovny to the series, after his departure following the eighth season finale "Existence".

The genesis for the episode was a storyline Duchovny had developed during the series' eighth season; he originally pitched an idea featuring a mysteriously disfigured person introducing himself to Scully and admitting that he possessed a connection to Mulder.

In the teaser, a couple, the Van De Kamps (Adam Nelson and Shannon Hile), adopt Dana Scully's (Gillian Anderson) infant son, William (James and Travis Riker).

It is revealed that he is actually Jeffrey Spender, a former FBI agent supposedly killed by The Smoking Man (William B. Davis) three years earlier.

Spender says that he acted out of his hatred for his father, since the new conspiracy was created by The Smoking Man after the alien rebels burned the original group.

[3][4] "William" marked the return of David Duchovny, in some capacity, to the series, after his departure following the eighth season finale "Existence".

He had originally pitched an idea featuring a mysteriously disfigured person introducing himself to Scully and admitting that he has a connection to Mulder.

Duchovny, Anderson, and executive producer John Shiban were not happy with this turn of events, due to them being parents and feeling that the action was not realistic.

[10] Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode three stars out of five.

[11] Tom Kessenich, in his book Examinations, wrote a largely negative review of the episode and derided its plot.

Crang, in his book Denying the Truth: Revisiting The X-Files after 9/11, praised the decision to conclude the William subplot but called the episode's conclusion "sappy".