Darwin Watterson is a member of the Wattersons. He used to be Gumball 's pet goldfish, until one day he started to grow legs, speak, and eat other foods that are not fish flakes, and became Gumball's best friend.
Darwin is a goldfish with legs. His goldfish-shaped head takes up his entire body, with his fins and legs hanging down from it. He has retained his goldfish tail and fins, the latter of which he now uses as arms and hands. His legs are much longer than his body, ending with plain feet matching the color and texture of the rest of his body. Usually, though, he covers them with green and white sneakers. These shoes are the only pieces of clothing he wears - a common misconception is that he is also wearing a black shirt, but that is actually just a shadow casted by his big head.
Darwin apparently has thick coatings of blubber, making him resistant to pain. The blubber's radius is about the length of Gumball's arm, as shown in The DVD, where Gumball had to sink his whole arm into Darwin's head just to reach his cheekbone.
Due to his sudden entrance into the world, his world view is somewhat skewed and naive. He has trouble understanding many situations. Often people have to explain things to him, like when he didn't understand dates and when he used a DVD as a pizza cutter.
He also 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 four numbers he knows are 7, 5, 2, and 9. Also, in The Mystery, he fails to remember anything he did the day before, while all of his other classmates remembered clearly.
Despite having legs and human-like abilities such as breathing air and eating normal food, Darwin still sleeps in his fishbowl. However, because he has grown in size, he is rather squished in the fish bowl and takes the shape of it. He also still seems to like fish flakes, as he took a snack break with some fish flakes when the house was flooded in The Responsible. He has been shown that he likes to eat a lot. He particularly likes fish flakes, but he is also fond of cookies, chips and ice cream.
Throughout the series, Darwin has referred to Mr. and Mrs. Watterson as "Mrs. Mom" and "Mr. Dad". Whether this is because he shows more respect for them than a child would, or just the fact that he has a slight questionality of them as 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.
Darwin tends to follow Gumball's advice and suggestions, despite them being stupid and childish suggestions. Gumball is not a very good influence on Darwin.
Hilariously, Darwin appears to be somewhat of a ladies' man. He is chosen by Masami to be her "boyfriend", and got a kiss on the cheek from Rachael, who is an upperclassman.
- "I want more kids!"
- "Your silence says a thousand words!"
- "Just stand on the sidewalk, dude."
- "She dropped her button!'
- "I always thought I'd make a good model."
- "Maybe it's because of my perfect skin."
- "I thought it was beautiful!"
- "She will be mine!"
- Darwin: "What happed to your clothes?"
Richard: "I ate them!"
- "What's a Date?...hey!"
- "Oh, did I say the 'Leap of Faith'? I meant, the 'Leap of Filth'!"
- Gumball: "...half shark, half bear, half alligator!"
- "The shower of slime!"
- Gumball: "What does a warrior need for a good warmup?"
Darwin: "Mittens and a scarf?"
- "Yes, Mrs. Mom!"
- Gumball: "I covered his way in!"
Darwin: "And I covered our way out!"
- "Um, Two! Seven! Nine! Well, that's all the numbers I know! Try two again!"
- Darwin: "Oh, can I borrow ten bucks?"
Gumball: [reluctantly hands him ten dollars]
Darwin: Thanks! Wait for me Tobias!"
- "Okay, I didn't mean it - boyfriend joke! Look, I'm laughing! [fakes laughing] You can stop crying now! Please?"
- "What's a date?"
- [after being kissed on the cheek] "Everything is so clear now!"
- [cheerfully] "I feel awkward!"
- "Why is it called 2000, anyways?! It's not like it's the future anymore!"
- [gruff voice] "I don't care that you're sad, Jimmy, it's store policy."
- Gumball: "What was that!?"
Darwin: [sheepishly] "It's my tummy."
- Gumball: "I thought you ran away forever."
Darwin: [whispers] "I got hungry!"
- Darwin seems to be able to speak Cantonese, but says he couldn't in a complex sentence, as shown in The DVD. He said "Cantonese is a hard language, so no."
- Darwin's wide fish body casts a shadow on his arms and legs that has, on occasion, been mistaken for clothing.
- Darwin can breathe in any water, but for the sake of fitting in, holds his breath while submerged.
- Darwin's fat protects him from a lot of damage.
- In The Dress we see that he's also left handed when he's drawing Gumball in the dress.
- On an exclusive video on the official "Elmore Stream-It" YouTube page, it is revealed that Darwin can exhale for much longer than Gumball can.
- Darwin is a child character voiced by a child voice actor, like Gumball.
- In The Party, he called himself Darwin Raglin Caspian Ahab Poseidon Nicodemus Watterson III - this is a spoof of Pippi Longstocking. If this is his full name, then that would mean Gumball had two other fish as pets before Darwin and they had the same name.
- The only numbers he knows are 2, 7, 5, and 9.
- Many fans believe that Rachel could be a possible love interest, even though obviously she was amazed with his talents on the spot and was rather taken back by the punishment she wouldn't receive. Logically, the kiss she gave him was a friendly thank-you kiss to a cute little kid, not an actual boyfriend kiss.
- Despite the fact that Darwin is a fish, in The Responsible, Gumball & Darwin put a fish in bread on Anais' plate.
- Darwin can open his head to show his brain as shown in The Goons.
- Darwin won the Dumb Race.
- Darwin can't use the bathroom unless Gumball whistles for him.
- It's possible that Darwin got his name from the famous scientist Charles Darwin who came up with "The Theory of Evolution". And Darwin seems to have gone through evolution. And Cartoon Network said Darwin got legs like fish did to adapt to land.