Cuphead secrets

There are 4 short cuts, one for each isle.

Isle 1: Next to the Goopy Le Grande Boss fight om the right.
Isle 2: Behind the mountain near wally warbles
Isle 3: Go through the fence near the crane and around the junk pile. This is near junkyard jive.
Isle 4: Through the area between and tree the waterfall on the right.

Isle 1: After completing the game, go to the NPC on the left of Cagney Carnation. Behind the trees if you look you will see the coin. Go through those trees and get the coin.

Isle 2: Behind Funhouse Frazzle run at the right side of the green cart. Talk to the girl near Fun fair fever and then use the aforementioned isle 2 shortcut. Talk to her again, and you get a coin. Talk to the juggling guy next to Grim Matchstick and then get 4 parries in a row (any level). Then talk to him again.

Isle 3: Behind the booth that is behind Porkrind's shop. Run left and ram into the left side wall, and you'll get a coin.

Isle 4: Keep walking forward behind Porkrind's shop. Keep running behind all of the stores until you get your coin.

Inkwell Hell

Behind the left dice stack.

Black and white + Vintage sound
Talk to the turtle on the dock in Isle 3, Then beat every run n gun without killing anything (parries allowed)

2 - strip
Talk to the fork man in Isle 3 and get an A- on every boss. It's ok to have a few B's.

Golden Ms. chalice
Talk to the cactus lady in Isle 4 and beat the game with Ms Chalice (any difficulty). Talk to cactus lady, and you get the filter (her fire will be lit when you can get the filter.)

All of these can be used in the visual mode (except vintage sound which in in audio.)

Root Pack: Don't shoot the onion when he appears.
Djimmi: Turn tiny when he scans you (before the puppet phase).
Sally stageplay: Parry and bounce or double jump (Ms chalice) and stand on both of those baby angel looking things.
Doggone Dogfight: Shoot all 4 puppies until their jetpacks start spewing grey smoke. (dont kill any)