Hint: Spin jump:
When the game starts, jump on the plant over the bellhop, then jump on the ashtray and a pigeon. By jumping on the pigeon, you will be able to use a spin jump attack, which can push almost all enemies off screen.

Hint: Defeating: Harry and Marv:
Get the dart gun hidden in the Christmas tree in the last level. Use it to push them off the screen.