All power-ups:
Pause the game, then hold L + R and quickly press B, X, B, X, B, X(3), B(2), X, B(3).

All warp gates:
Pause the game, then hold L + R and quickly press X(2), B, X(2), B, X, B(3).

All FMV sequences:
Pause the game, then hold L + R and quickly press X(3), B(3), X, B, X.

View credits:
Pause the game, then hold L + R and quickly press X, B(2), X, B, X.

Defeating the Black Knight:
Ram the red switches when Black Knight moves near them.

Defeating the Funland Robot:
Ram him, then Super Slam him.

Defeating the Green Ghost:
Daphne will open coffins. When the Green Ghost hovers over an open coffin, Super Slam the switch. If Daphne opens a coffin and the ghost is above it, do a Thunder Smash on the button and the ghost will get sucked down. To get the ghost to go in all the way, you must do this three times.

Defeating Master Mind
He will send out robots and space kooks. Defeat them and when the electric field is down, ram the red switches, Keep repeating this until he falls off his platform. Then, dodge his robots and supersmash them. When the electric field is down again, ram the two red switches and repeat two more times.

Defeating Red Beard's Ghost:
Red Beard will send out ghosts. Dodge them, then a ghost of Captain Moody will appear. He will throw his sword. Go to one of the ropes, stay until the knife cuts it, and keep repeating this attack.

Help from Shaggy in Dark And Stormy Night Part 2:
If you die after getting all the keys and having Shaggy up in the coffins, when you restart the level you can talk to an invisible Shaggy and still have him help you jump and walk around in his arms. You can take him all the way through the level to the doorway.

Holiday bonuses:
Change the Xbox system date to one of the following entries to see special things at the front yard and the mystic playground:

January 1: Fireworks
February 14: Hearts on Scooby Snacks
March 17: Green fountain water and smoke from chimneys
July 4: Red, white, and blue fireworks, fountain water, and smoke from chimneys
October 31: Giant bats over courtyard door for decoration
December 25: Snow
December 31: Fireworks