Blue

Blue is a dog that a owns.

History
He was once seen lying on Homer's command console at the power plant.

The hobo once wiped water off of Lenny's squeegee and poured it into a dish for Blue to drink.

Non-canon
When Homer turned into a giant blob that devoured many people in Springfield, Mayor Quimby decided to use Homer to get rid of the city's homeless problem. The Mayor had Homer hide in a homeless shelter so that when the homeless people entered the building they were immediately devoured. One of the was about to walk in, when his dog, Blue, started barking. As the hobo wondered what Blue was barking at, Mayor Quimby shoved the man inside the shelter and Blue ran away.

Trivia

 * In every episode he's appeared in, Blue has been colored differently.