Not sure if that is a joke but i have definitely had 'i watch youh while you sleep ' lol
The English Wiktionary is wrong in this matter. The Polish one clearly states that it should be accusative.
A clever problem that's hard to imagine in a realistic context. But… you can either try the exact same sentence as above, or you could specify it by saying „Widzę was z powodu okna”.
„Okno” is neuter, so it should be „wasze” (or „twoje”, as appropriate). Of course that's assuming the object you see was somehow specified in the context, because that's what would the verb „widzieć” would expect (unless we are talking about seeing as opposote to literally being blind). For looking at nothing in particular through the window you would use the verb „patrzę”.
Why is it not "przez okna" in this case? Shouldn't change the ending after a preposition?
No. „Was” is the genitive, accusative, and locative forms of „wy”.
„Wasz” is a separate word and behaves more like an adjective.
Yes, we do try to accept "you all" for every plural 'you', so that accepts "y'all" automatically. Added here.
If you don't know the context of its use, you wind up wrong as I do and it irritates me and then I get stupid. I hate making mistakes.