looking for bus to Anji (hello kitty theme park) from hangzhou fast train station and also back.

You must refer to the East Railway Station. Wel, take a taxi from the station to local North Bus Station to take a direct bus to Anji in 1-1.5h. At Anji Passenger Coach Center, there is special bus line leading to the theme park.

If you wanna go to the park directly from Shanghai, it is fine. Take a direct bus from the South Long-distance Bus Station to Anji in 3-4h. Then transfer to the special bus line to the park. After visiting, I'm afraid bus shall be the best way to go back to HZ.