Egg-Cerberus

The Egg Cerberus is the first boss faced by both Sonic and Shadow in Sonic the Hedgehog 06. Sonic faces it before the Dusty Desert level and Shadow faces it after the White Acropolis level.

Description
It is a giant dog-like robot, though its appearances in both Sonic and Shadow's stories lead to speculation on whether or not there is one or two of them. (Although the one in Shadow's battle seems wrecked, it could be the one from Sonic's story.) The bosses' defeat requires the player to grind on their headrest, hold on to its head antennae, and lead them into a wall.

Trivia

 * This robot is named after a dog in Greek mythology, Cerberus, who was a three-headed, fire-breathing, demonic dog who guarded the entrance to Hades' Underworld. However, the Egg Cerberus has only one head, unlike the Cerberus in mythology, which has three heads.
 * He bears a slight resemblance to the Metal Hound another Eggman robot made to resemble a dog.
 * In Sonic's battle it's referred to as Dr Eggman's 'pet' and in Shadow's battle it's his 'guard dog'. The Cerberus could have been demoted after a defeat by Sonic.