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Despite their radical difference in size, these two dogs have something in common - Gibson the Great Dane and Boo Boo the toy Chihuahua are both world record holders.

Measuring a whopping 107cm, gentle giant Gibson was named tallest dog back in 2004. Joining him in the hall of fame for 2007 is tiny Boo Boo who only measures 10.16cm tall and is smaller than Gibson's head.

The two celebrity hounds, who were both bred in America, met up to celebrate Guinness World Records Day 2007.

Boo Boo's owner Lana Elswick has bred Chihuahuas in Kentucky for 19 years and said she always knew her one-year-old pooch was special.

The tiny mutt was only about the size of a thumb when she was born; so small, in fact, that she had to be fed with an eye dropper every two hours before she could eventually nurse a bottle. Now she is a diminuitive diva.

"She has the attitude of a big dog she would let me know if anyone was around and she would try to guard me if she could," said Ms Elswick.

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Owner Sandy Hall lives with her dog Gibson in Sacramento, California. The Great Dane is also the world's tallest therapy dog and regularly visits children's hospitals.

"He just puts a smile on people's faces," Ms Hall said. "In one split second, people forget their cares and worries."