What is the most outlandish thing you’re OCD tricked you’re brain into believing?

I’ll go first, Hello 17m and I was fully convinced I was in another reality and nothing around me was real. This was a time where I was paranoid of schizophrenia and psychosis. This started happening when I went to Dave n Busters with my family and in my head I was like “what if you never left your room and this is playing in your head.” “You’re going insane” “you are alone and everyone is fake.” Even worse was I heard about some theory or some video shit when I was a kid I completely forgot what it was and in short and in simple terms it was kinda like. “Oh what if you’re living alone in the world and everyone and everything is fake and is just rocks and stones and nothing is real” no idea how I felt like this or even believed it and I feel much better. I’m still ruminating about it but I plan to go to therapy and hopefully get better. ALSO P.S any grounding techniques that work for you all?