Activate Power-ups
On the Pause screen, Hold L+R and enter: X, B, X, B, X, B, B, B, X, X, B, X, X, X. You will hear a sound confirmation if you entered the code correctly.
Dark And Stormy Night Part 2: Help From Shaggy
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.
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 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, superslam the switch.
Get The Football Helmet
To get the Football helmet go to the top of Haunted Hill.
Holiday Extras
Set the system date on your gamecube to one of the following days for holiday treats:
Jan 1st - Fireworks
July 4th - More fireworks
Oct 31st - Bats on door
Dec 25th - Snow pleasure
Unlock Aternate Credits Sequence
On the Pause screen, Hold L+R and enter: B, X, X, B, X, B. You will hear a sound confirmation if you entered the code correctly.