Keroberos aka Kero

Information:
Kero is the guardian of the seal, a magical fireblowing winged lion created by Clow Reed, the magician who created the Clow cards.
He is awoken from years of sleep when Sakura opens the Clow book in her basement and releases all the cards he was supposed to be guarding. She thinks he is a cool electronic toy at first and tries to work out where his batteries go!
Kero becomes Sakura's guide in recapturing all the cards and stays hidden in Sakura's bedroom and school bag.
He has a 'bedroom' in one of Sakura's drawers with extra special small furniture made from cardboard boxes.
Until the sun power cards Earthy and Firey have been recaptured, Kero is trapped in the small winged teddy bear form instead of his powerful lion form in order to not drain Sakura's powers. This is strange for him, he's used to being physically imposing and still has the attitude that goes with being a big creature. It's very humbling to have to be so small for a while.

He doesn't need to eat but he loves anything sweet especially pancakes and desserts. His sweet tooth is definitly his greatest weakness.
He's competive, whether it's in video gaming or in card capturing where he has to defend his choice of Sakura as potential Clow mistress against both Syaoran who feels that place should be his and Yue who feels that no-one can live up to their first master, Clow.
He does not get on well with Syaoran who expected Kero to be in his full form and didn't believe that a winged teddy could be worth much. He calls him the brat.
While Kero sometimes looks selfish in his greed for candy or in his competitiveness and may appear obnoxious, he is wise when it comes to the clow cards and their choice of new master and he has a very big heart: he helps Sakura to overcome her fears, he truly cares about her and is very good friends with Tomoyo.