Cerberus (ケルベロス, Keruberosu) is a fictional character in Clamp's manga and anime series Cardcaptor Sakura. His name is more commonly known in its Greek version, Keroberos, which is also often shortened to Kero-chan or just Kero.
He is voiced in his more common "hidden" form by Aya Hisakawa and Masaya Onosaka in his "true" form. He is voiced in the series by Matt Hill (borrowed form) and Richard Newman (true form), and in the second movie by Wendee Lee (borrowed form) and Dave Wittenberg (true form).
Keroberos's name and form are based on Cerberus from Greek mythology, a large three-headed beast who was assigned to guard the gates of Hades, a parallel to Cerberus’s duty in the Cardcaptor Sakura storyline where he guarded a deck of cards from the cover of the book that contained them.
In his borrowed form, Keroberos resembles a lion cub or rather a stuffed animal or a plush toy with yellow-orange fur, big ears, and small white wings.
However, his true form is that of a huge, tawny maneless lion or cougar, with enormous angelic white wings and chest-plate and helmet of beaten metal, studded with a large red precious stone.
By nature, Keroberos is bossy, demanding, and gluttonous, but he also genuinely cares about Sakura and believes that she will become the next Master of the Clow as he acts as her guide to gather the Cards.
He is responsible for giving Sakura the Sealing Wand, having appointed her to be the one to recapture the Cards she unknowingly released.
Kero's hobbies include playing video games and eating snacks and sweets (he loves sweets more than almost anything), even though, drawing his power from the sun, he generates his own energy, and does not need to eat to survive but unlike Yue, he enjoys the finer things in life.
He has a particular fondness for cake, cookies, and chocolates. In the anime, he was also intoxicated by a box of brandy chocolates, causing him to become drunk.