7 Lives (Japan-only):
When you have no more lives left, press Start to pause the game, then hold Up, press A, press B, release Up, hold Right, press B, release Right, hold Up, press A, release Up, hold Left, press B, release Left, hold Down, press B twice, release Down, hold Right, and press A.
Skip to Week 900:
At the title screen, press Left nine times, Right five times, A once, B once, A once, and B once. Then hold A, B, Select, and Start to be able to skip straight to the 900th week.