During his first few phases, Ug manifests as a Tyrannosaurus Rex. His second form appears after his first few phases: a yellow-skinned, fat humanoid. His hair is very short. His weapon is a club that lets him cause a huge shockwave.
Luigi finds Blue Toad inside room upon making his way in, he tries to release him from the portrait. However, Ug, now manifesting as a T-Rex's reanimated skeleton, comes up behind his back and attacks him and eats the whole portrait and hides it inside his skeleton, so Luigi has to destroy him. However, Ug is revealed to be just some other ghost.
At the end of the game, it is revealed that most ghosts in the hotel were brainwashed by King Boo, and thus were unwillling accomplices. Thus, this might also be true for Ug. However, his eventual fate remains unknown.
Phases 1 through 3
Luigi has to fight Ug's T-Rex form by throwing him artificial dinosaur eggs that will have stuck on his mouth, this makes the T-Rex reveal his core and Luigi has to throw another egg at it, causing damage to the boss. Ug will try to cause some rocks from the ceiling to fall on Luigi. When Luigi hits the T-Rex for the second time, Ug uses his strength to finally break free from his restraints and goes on his way around the room to kill Luigi. Gooigi can be summoned to take care of the dinosaur by using the rest of the fossils that the T-Rex destroyed to throw them at it. After damaging it enough, the T-Rex will finally collapse and be destroyed, at which Ug reveals his true form.
However, a caveman ghost emerges from the ruins of the skeleton, revealing himself as the one possessing it the whole time. He is angered at Luigi for destroying the T-Rex and prepares to battle him with his massive bone that uses as club. Ug will swing his bone to harm Luigi and even charge and slam at the floor creating an energy wave that damages everything and everyone on the ground. In order to defeat Ug, Luigi has to flash Ug in the right moment he gets his club stuck to the ground which allows Luigi to vacuum him. After getting defeated, Ug will throw his club in the air and humorously have the club land on his still-exposed head before being the device sucks him in. After Blue Toad is released, he reveals having the elevator button to Basement 2, where Chief Mechanic Clem resides.
- Ug is the second boss in the game to possess something. He does this during his first three phases by possessing the T-Rex skeleton statue.
- Though his real name is Ug, in the Dutch translation of the game he is literally called T-Rex.
- He somehow resembles Marvel's superhero Hulk given his short hair, green skin and massive strength.
Luigi's Mansion: Dark Moon
Luigi's Mansion 3