"Like you, I recently learned that ours is but a single dimension in a multiverse of dimensions. Intrigued, I used this very portal to survey them all. Which is when I made a startling, horrible discovery. There are not simply eight of you, but...SCORES of you! BEHOLD: a multiverse of accursed Teenage Mutant Ninja Turtles!"
— Shredder / Ch'rell, Turtles Forever
Penny: What's a Multiverse?
"There is not one universe. There are many: A multiverse. We have the technology to travel between universes, but travel is highly restricted and policed. There is not one you. There are many. Each of us exists in present time, in parallel universes. There was balance in the system, but now a force exists who seeks to destroy the balance so he can become The One."
— Narrator, The One