The people of the main Toobworld think of the cartoons that we watch in the real world as cartoons as well, even though some of those animated characters have crossed over into the live action TV universe on occasion.
And it works in reverse as well.
In the annual Halloween episode of 'The Simpsons' this past Sunday, Homer Simpson mentioned that he got the 'Seinfeld' boxed set for Season Seven. So to the citizenry of the Tooniverse, the people of Earth Prime-Time are just characters in a TV show.
Granted, the "Treehouse Of Horrors" specials are not officially part of the Simpsons' corner of the Tooniverse, but so what? Beat it kid, ya bother me!