S9E7: Road to the North Pole
Interesting. Interesting theory, Brian.
Who else isn't real, hmm?
You gonna tell me that Elmo isn't real? Huh?
SpongeBob? Is he not real, Brian?
Is SpongeBob not there at the bottom of the ocean giving Squidward the business, hmm?
And what about Curious George? Huh?
Does he not really exist?