Here, Darwin flakes out on defending Gumball from Tina after he says that her playing the piano is useless due to her tiny hands. He claims that he did it because he was teaching him a lesson about crushing the piano dreams of a young T-rex, but I like to believe he did it because he's a dirty COWARD.

In the beginning, we can see Darwin running away from Tina along with Gumball. Why would he be running if she was specifically targeting Gumball for making fun of her? My theory is that he's a hypocrite who called her out along with Gumball and only fled because he didn't want to face a giant T-rex. For if he stayed, he would have gotten his butt kicked along with Gumball.

For the rest of the episode, he complains about Gumball doing a bad thing and refusing to accept the consequences of it, when he is just as guilty himself. I believe he is only venting out these frustrations as a mask to cover up his own guilt.

He even says outright that he shouldn't be bothered to fight a T-rex. This is why I believe that Darwin is just a coward and was too scared to help his brother in the flakers. (end of post)