Twin Peaks Files

In the X-Files' season-three episode "Redmption," Kenneth Welsh plays a servant of the devil. In Twin Peaks, he plays the near-demonic ex-F.B.I. agent Windom Earle.
In "Redemption," a character with "visionary" insight loses said insight because his dose of haloperidol has been increased.
In Twin Peaks, haloperidol is used by Phillip Gerard; only when denied it can he become his true self, Mike of the Lodges, and point to Laura's killer.
Though possibly coincidental, I think it's interesting that haloperidol comes into play in the X-Files episode with another Twin Peaks character.
FWIW: Season Three of X-Files also features Roger Cross, who plays Curtis Manning on "24." He's also in three other X-Files episodes.