Hobbes is a close friend of Calvin's, and his only true confidant. However, he usually is in a stuffed tiger form to retain his powerful and dangerous urges. He is a tiger, but can walk bipedal and use his thumbs.
Like Calvin, he is from the comic stripe, and also has two additional forms. The first is Fire Tiger, which is as its name denotes, a tiger made of flames. His second form is a mechanical creature that reminds me slightly like Fury Turquoise. However, this form has three crests on his forehead and two jets on his back.