Go to the dock in Mario Stadium. Look for a little whirlpool on it. Have Princess Peach use her heart power on it.
OR
Beat all the practice modes.

this is a very good blooper

Super Mario Bros. <strong>Blooper</strong> Keychain Charm

The blooper charm measures about 1 inch. This can go on zippers, key chains, cell phones, back packs and much more.

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Blooper: ~3.9


~3.9″ Nintendo DS Stylus features characters from Super Marios at the top of the stylus. NOTE: Due to the unique design of each figure, the actual size of the product may be slightly smaller or bigger than stated. This series is made up of 6 styluses (EACH SOLD SEPARATELY): 1Up Mushroom, Blooper, Boo, Cheep Cheep, Goomba, and Turtle Shell. Contains small parts. Recommended for age 8 or up only. This product is imported from Japan. Like many US products, it’s made in China. Meet the Japanese ST “Safe Toy” standard. To purchase other styluses from the series, search for: 1Up Mushroom (T9899999988342), Blooper (T9899999988335), Boo (T9899999988328), Cheep Cheep (T9899999988311), Goomba (T9899999988304), Turtle Shell (T9899999988298).

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please please please be specific i really really need help on how to unlock them i think you do something in challange mode right?

Super Mario Bros. <strong>Blooper</strong> Octopus Plush Keychain

Imported from Japan. The Mario Bros. key chain measures approximately 3-inches. Made by Banpresto.

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Mario Cart Wii Power-up Charms - <strong>Bloopers</strong>
No description for this product could be found, but have a look over at Amazon for reviews and other information.
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Blooper is a 10 tailed squid and he is white.