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.

Product Description
The blooper charm measures about 1 inch. This can go on zippers, key chains, cell phones, back packs and much more.
Buy Super Mario Bros. Blooper Keychain Charm at Amazon

Product Description
~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).
Buy Blooper: ~3.9″ Super Mario DS Stylus at Amazon
please please please be specific i really really need help on how to unlock them i think you do something in challange mode right?

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