5 extra lives easy
First, go onto World 1-1 and play the beginning normally.
When you get to the part with the mega mushroom, don't just grab it. Wait until it is on the very edge of the cliff to grab it. If your timing is right and you keep moving forward, your "big-ness" should last until the end of the level, letting you destroy the staircase and even the flag, which give you 5 extra lives. Enjoy!
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