Targeting 3- to 6-year-olds, the series explores the world's many mysteries above and below water in a unique and entertaining way.
Its characters include:
- Secret Agent Fishtronaut, a fish who wears flying armour to survive and interact with beings outside water.
- Marina, a human tomboyish girl
- Zeek, a monkey
- Billy and Mac, twins and innocent trouble-makers.
Fishtronaut has examples of:
- 2D Visuals, 3D Effects: The P.O.P. was very obviously done in CGI. The rest of the show looks to be animated in Flash.
- Action Girl: Marina, but the action is limited to searching for more clues in the park.
- Animation Bump: The animation in the first season is very choppy and stiff; the second season's animation is way more fluid, and the change is not gradual.
- Artistic License – Biology: Even though most of the animals were designed correctly, for whatever reason, beavers are shown with long snouts and stubby tails, while real beavers don't have snouts, and have long, flat tails.
- Balloon Belly: When Zeek eats too much of anything. Happy Plumb also gets one, always.
- The Case of...: Every episode has this in the title.
- Catchphrase: Fishtronaut usually shouts "Galloping guppies! note We figured out the clues!" and "Teamwork is fantastic!" whenever a mystery is solved.
- Crazy-Prepared: Fishtronaut has anything you can imagine within his little armour.
- Dresses the Same: While at a costume party, Rosy Barb is seen wearing a costume that looks like Fishtronaut's suit, and she cheerfully says, "I bet no one else has thought of this!" Cue Happy Plumb wearing the same costume.
- Early-Installment Weirdness:
- As mentioned above, the animation of the first season was very choppy, and it greatly improved in the second season.
- Some of the early plotlines were much more simple than what would come later. For example, the early episode "The Case of Mistaken Identities" is about Marina thinking about a bunch of animals has disappeared when it turns out they had actually just camouflaged themselves. Compare that to the later episode "The Case of the Crazy Deliveries", where Zeek finds a bike at the post office and decides to deliver packages to all the animals in the park, only to get them all mixed up, while Fishtronaut and Marina try to find him so they can solve the case, which was about the mixed-up packages.
- Most of the earlier episodes included a sequence where Fishtronaut had to refill the oxygen tank on his suit, represented by a bar on the side of the screen with six circles full of water slowly draining out. This started to become phased out later in the first season and was almost gone entirely by the second.
- The characters would talk to the viewer more often in the early days, to the point where Marina often invokes Fake Interactivity. In later episodes, they only do this when opening the P.O.P.
- There is a Running Gag where Zeek comes up with an outlandish guess as to what the clues mean just after the team receives them. He didn't do this in the early episodes.
- Failed a Spot Check: One episode starts with Fishtronaut looking for a pair of goggles, not realizing that he is also wearing them.
- Flying Flightless Bird: "The Case That Fell From The Sky" has a variation; The trio deals with a chicken who keeps trying to fly, and have to tell her that it's not worth it. It isn't until Fishtronaut shows her what it would be like to fly that the chicken realizes she doesn't want to fly anymore.
- Fun with Acronyms: The Primary Objective Pod, the multicolored ball that gives out the clues.
- Gadgeteer Genius: Fishtronaut invents all of gadgets that can be used to solve the mysteries. He also built the Bubblex suit by himself.
- Green Aesop: Since the whole show is fundamentally based around teaching kids about the environment, you can expect this to come up pretty often.
- Idiosyncratic Episode Naming: Every episode is titled "The Case of the <X>", or "The <X> Case".
- Idiosyncratic Wipes: All of the scene transitions involve leaves (or some other natural object) briefly obscuring the screen.
- Lovable Coward: Zeek is very much afraid of a lot of things, but still manages to help solve the mysteries.
- MacGyvering: A lot of Fishtronaut's inventions are made using spare parts just lying around.
- Mobile Fishbowl: Fishtronaut's Bubblex suit is designed for him to safely go out of the lake, which means it's full of water.
- The Movie: This show actually has two of them; The first was Fishtronaut, Secret Agent of S.E.A. from 2012, which was pretty much just a compilation of episodes from the series. The second was Fishtronaut: The Movie from 2018, where Fishtronaut, Marina and Zeek investigate an abandoned, polluted city.
- No Fourth Wall: The characters always invite the viewers to help open the "pop" ball containing the initial clues.
- Once per Episode: Every episode has a sequence of the P.O.P. breaking out a clam underwater, getting to the characters, and the characters opening the P.O.P. by "dancing" to the rhythm it makes.
- Poor Communication Kills: "The Case of the End of the World"; While playing hide and seek, Zeek overhears Dr. Green and Dr. Takeshi talking about a solar eclipse that was about to happen, and believes that it would cause the world to end. He decides against telling Marina and Fishtronaut because that would cause him to lose the game, so he decides to warn all the other animals in the park, causing them to panic, and giving Marina and Fishtronaut their mystery of the day.
- Puzzling Platypus: The focus of "The Case of the Lost Critter" is a baby platypus that got separated by its mother. Of course, none of the characters have heard of platypi before, initially thinking they were "weird ducks", so this case is where they first learn about them.
- Replaced the Theme Tune: The show got a new opening sequence in the second season. The new theme song is basically the same as the old one, but with different lyrics.
- Retool: In addition to the Animation Bump mentioned above, there were several changes between the first and second seasons:
- In the first season, the P.O.P. only played simple rhythms which the characters had to replicate in order to open it. In the second season, the P.O.P. played actual music, which the characters had to dance to in order to open it.
- The second season started including musical interludes to go along with certain montages.
- Riddle Me This: Whenever Fishtronaut gets help from Happy Plumb, he always gets an answer in the form of a riddle. Fortunately, the riddles always help him solve the case when he figures it out.
- Strictly Formula: Every episode goes through one basic plotline: The characters discover a mystery, which usually involves helping another animal at the park, and open a P.O.P. that gives them two clues that help them solve it. Then after the mystery is solved, everyone opens another P.O.P. that gives them something as a reward for solving the mystery.
- Suspiciously Specific Denial: In "The Case of the Flying Leaves", Billy and Mac spend most of the episode collecting all the paper in the park to build a giant paper airplane. When the main trio comes across their treehouse looking to see what they need the paper for, they act like there is no paper there, while the treehouse is filled with paper.
- Talking Animal: Almost the entire crew. The only recurring humans are Marina, her uncle Dr. Green and the twins.
- Tin-Can Telephone: One of the clues in "The Case of the End of the World", which is meant to represent the miscommunication that fuels the plot.
- Tomboy: Marina somewhat dresses like a boy, although she has prominent lipstick lips.
- Trademark Favorite Food: Zeek is a monkey, so he's contractually obligated to be obsessed with bananas.
- Uncanny Family Resemblance: "The Case of the Other Fishtronaut" introduces Fishtronaut's cousin Fishter, who looks just like Fishtronaut, but with blue eyes and red stripes on his fins. Naturally, when Fishter takes the Bubblex suit and goes out into the park, no one can tell the difference.
- Vocal Evolution: Fishtronaut's voice was slightly higher-pitched in the earlier episodes, at least in the English dub.
- Where the Hell Is Springfield?: The show is set in Smiling Trees Park, which is heavily implied to be in Brazil. However, Brazil is a huge country, and there aren't many clues as to where exactly it could be.
