What if Sans’s telescope prank wasn’t only a prank, but also a test?
Normally, the kind of prank where you trick someone into getting a mark on their face is a stealth one. The embarrassment is through them not realising the mark and going on with their lives until someone else decides to tell them, or they look in a mirror eventually. They also realise they were the ones who participated, unknowingly, in getting a silly mark.
In this scenario, everyone basically yells SANS and tries to call him on it, resulting in him joking about a refund. But there’s no way Frisk would know about the eye blotch. The normal run of the joke would be for Frisk to obliviously carry on until they find a mirror somewhere. Instead, most people confront Sans immediately.
Maybe he was testing to see if we, the player, really were there. Frisk could’ve turned on him and called him on the prank… despite having no way to know they’ve got a pink eye. That’s what WE know. We outed our existence to Sans.
This is an interesting theory, but, I have something that may counter it. Frisk looked into the telescope and saw red all over when they did. Even though they might not know that the mark is on their eye, they do know that there was nothing to see in the telescope. So this might just be something along the lines of Frisk telling Sans, “The telescope doesn’t work,” or “Something’s wrong with your telescope.” I like this theory, but I just wanted to point it out.
AngelMihe 