The Obese Pig is a very powerful pig. If you hit it's ginormous stomach, the bird shall bounce off (unless it is the Mighty Eagle!), dealing only a very tiny amount of damage to the pig. However, its top takes twice the normal damage.
This pig appears in Angry Birds Space: Utopia 2, being almost as strong as the King Pig (His strength is 96/100, the king pig's strength is 100/100). Obese Pig also appears in Angry Birds Seasons 5 in Snow of the snorkers, starting from level 1-4.
He also appears in Angry Birds TNT as a boss. Obese Pig will wear the King Pig's crown, making some think he's a giant King Pig in this state. He is in Angry Birds Generations. Obese Pig is also in the game Angry Birds 1 ½, and in Angry Pigs (Gold2232) he is a hypnotised pig and boss. If you try to throw birds at him (except Fire Bomb Bird and Space Terence) they bounce back.