1. In season 4, an episode shows a character going back in time to the events that occurred during the pilot episode. Even though the character was not in the pilot episode, this S4 episode implies that they were there in the background, off-camera, the entire time, and playing a pivotal role in the events that kicked off the series.
2. If you watch a certain scene in the actual pilot episode, you can briefly see that character's shadow in the background, implying that the creators had actually planned these time travel shenanigans from the beginning.
3. Many fans claim that the shadow was not actually in the pilot when it was first aired; that it was only added in reruns and home releases after that S4 episode was written. Other fans claim to have a home-taped recording of the very original broadcast and that they do see the shadow.
4. The person that made this video came across a social media post where a user showed off a pre-release promotional tape of the pilot episode. They contacted the user and purchased the tape for an undisclosed amount.
5. After a drawn out sequence detailing their multi-camera setup used to record the tape playing on their TV (in an attempt to prove nothing is being faked), we see that the shadow does indeed appear in the scene just as it does in all reruns, etc.

Yes.