FACT. The Count lives in a large, Gothic-ish castle on a lonely hillside.
FACT. There are no large, Gothic-ish castles upon lonely hillsides in New York City.
FACT. The Count does not have a job in the city.
THUS. The Count has no actual reason to enter into New York City bar his own wishes.
FACT. The child cast of Sesame Street changes frequently and widely. You rarely see the same kids on the show for more than three or four episodes.
FACT. However, the adult cast of Sesame Street changes very, very rarely.
FACT. Everybody seems to take the fact that a vampire is wandering a New York City street with surprising calm.
THUS. We can extrapolate:
The Count travels into the city to feed upon the children of Sesame Street, and the adults of Sesame Street are his willing slaves.