I am a HUGE supporter of the Stan's Twin Theory, and I am hyping up Not What He Seems because it could be the episode where this popular theory is actually confirmed.
If there's anyone who doesn't know what this theory is, to make a long story short, Stan has a twin, Stanley, who mysteriously vanished in 1982 due to unknown reasons, presumably pulled into the portal. I recommend watching the videos by Vailskibum94 on YouTube if you want to know more and see the evidence behind this.
So what do you think? Will March 9th bring the confirmation of this theory, or will it be something different?