The real Book of Shadows prop was being repaired during the filming of this episode. Tanya was flipping through pages of a different book and the cameras simply avoided showing the book's cover to hide this.
The title of this episode is a nod to anther supernatural series The X-Files (1993). Which used the tagline, "The Truth is Out There" for the majority of the series.
The first introduction to time travel in the series.
When Piper accidentally knocks over the cereal box, she freezes time to move the trash in place, when she could've saved the box. Once the trash is moved, time would unfreeze automatically.