To change costumes, enter Jack's closet in his house.

After losing your lives and the continue screen appears, try to stop the timer at the following times to get the corresponding bonus:

7.77: 500 souls
6.66: Single blinking pumpkin, no souls lost, but no full health
0.01: 500 souls, Crystal Bottles, Blue Souls, and Red Souls refilled (if you have a Gold Pumpkin)

Beat the game once

Get an "S" rank on all levels and do both secret chapters

Beat the game once

Beat the spider boss

Beat the Docter

Get an "A" rank on all levels