Darwin

Due to his sudden entrance into the world, his perspective of it is somewhat skewed and naïve. He has trouble understanding many situations. Often people have to point out his misconceptions and faults, such as the time he didn't know the definition of dates, and when he used a DVD as a pizza cutter.

Darwin is an overall happy person, sharing his best friend Gumball's optimistic view of life. His cheery personality shows in several episodes, most notably in "The Flower," where he was immune to the effects of Jealousy, due to being completely satisfied with his life. However, his jealousy is triggered when Gumball and Penny start dating, as seen in "The Burden" and "The Bros," causing him to go desperate lengths to break Gumball and Penny up in the latter. It takes a lot to trigger a negative reaction from him, but when provoked far enough, he can get very intense. A good example is in "The Banana," where he trashed Banana Joe's locker, and threatened grievous bodily harm to him, all in retaliation for his pen being chewed, and his homework getting ripped. Incentives also seem to fuel him up, like in "The Fridge," where he repeatedly smashed a ball into Gumball's face, all for the sake of a top spot on the fridge.

Darwin's happiness may just be a façade, though, as in "The Words," it is shown that people actually annoy him a lot; he just hesitates to tell them off. With help from Gumball, though, he begins telling people, often with intense hostility, everything he hates about them. Another example is in "The Limit"; when Darwin, Gumball and Anais were all sulking, and upset over having their day wasted going to the mall without any treats, Darwin wanted to retaliate against Nicole for this, by destroying the car, and tricking her into believing the three all died in it. He initially claimed to be a "paci-fish" in "The Ghost" which he contradicts in later episodes (even later on in the same one).

Darwin has poor memory, likely based on the misconception that fish have a memory of only three seconds. To him, basic spelling is complex, and the only numbers he knows are 2, 7, and 9. Also, in "The Mystery," he fails to remember anything he did the day before, while all of his other classmates remembers clearly.

Despite being human-like, Darwin still sleeps in his fishbowl; however, because he has grown in size, he gets rather squished in there. He also still seems fond of fish flakes, as shown in "The Responsible," and "The Picnic." Other foods he enjoys are cookies, chips, and ice cream.

Throughout the series, Darwin has referred to Richard and Nicole as "Mr. Dad," and "Mrs. Mom," although at some points, he calls them "Mom" and "Dad." Whether this is because he shows more respect for them than a child would, or just the fact that he has some doubts of them being his "parents" is anyone's guess.

Darwin falls in love at first sight with anything that wears a pretty dress. An example of that would be in "The Dress," where he saw Gumball in a dress, and completely fell in love, thinking he was a girl. At that time, he was so in love that he said to the "girl": "I love you", and a photo of him trying to kiss "her" was shown. When the dress later fell onto a fire hydrant, Darwin then fell in love with it. Humorously, Darwin appears to be somewhat of a ladies' man. He has already had three romantic encounters: one with Masami, another with Rachel, and a third with Carrie. Masami chose him as her fake boyfriend, and even went so far as to kiss him. Rachel gave him a kiss on the cheek after he cheered her up at her party. Carrie received a spontaneous kiss from him, with him saying that he has wanted to do that for a long time. He's also shown to be somewhat smooth as to talking to women as shown in "The Bet," when Bobert repeated what Darwin told him to say, Tina was seduced.

In Season 2, Darwin is shown to be angered very easily, and resorts to acts of violence, which have in a few instances bordered on sociopathy.

Also, in Season 2, Darwin becomes more conscientious, as he would sometimes call Gumball out for his wrongdoings, such as his taking advantage of Bobert in "The Bet," and his being insensitive to Banana Joe in "The Promise." As stated in "The Sidekick," Gumball considers Darwin his "guardian," meaning he is the one who keeps him from making bad decisions.