Tyrannosaurus

Tyrannosaurus (ティラノサウルス) is the name of a small mouse that Iceburg found and takes care of.

Appearance
Tyrannosaurus is a small, white mouse, with a long tail, red eyes, and a cheerful look on his face.

Most of the time he stands on his rear legs, keeping his front legs raised in a standard mouse pose resembling a Tyrannosaurus Rex, which probably gave him his name.

Over the last two years, he has grown to several times his original size, going from being able to fit in Iceburg's pocket to about the size of his master's head.

After the 2 year Time skip he is seen wearing a collar.

Personality
Tyrannosaurus spends most of his time lying in Iceburg's pocket and squeaking happily when his master caresses him.

He is apparently very loyal and attached to Iceburg, as he is always seen with him. During the fire at Galley-La Company's HQ, instead of running away, he remained by his master's side, trying to wake him up with his squeaks in order to save him.

History
Tyrannosaurus is always seen together with Iceburg, he appeared the first time in his pocket, when Mikazuki was bothering Paulie at Dock 1, before being defeated by him and the other carpenters along with his crew.

During Iceburg's convalescence, he was always by his side, standing on his bed.

Later, during the fire at the company's HQ at the hands of the CP9, instead of running away, he tried to wake up Iceburg, without success. He, alongside his master and Paulie, were fortunately saved by Tony Tony Chopper, and he spent all his others appearances together with Galley-La's president.

He was last seen during Iceburg's audition for a new secretary, on the Cover of Chapter 487, lying as usual in his master's pocket.

Two years later he is still with Iceburg and his 10 years old secretary.

Two Years Later
He was seen next to Iceburg and his new secretary.

Trivia

 * Tyrannosaurus was picked up by Iceburg not long before the meeting with Luffy. Iceburg also gave him his name during that occasion.