Prismo ponders how Fionna and Cake got into Ooo and goes to check Simon's mind, only to find he cannot access it. Prismo: "Okay no thats just weird"

He teleports Simon, who was in the middle of a shower into the Time Room, Fionna and cake quickly cover there eyes

After giving him some clothes, Prismo interrogates Simon over how Fionna and Cake got into Ooo.

Simon: "wait fionna and cake are real?!"