He’s one of the last Boopkins, the other being his dad. He first appeared in SMG4 N' Pals: Seaside Stupidity Part 1 after SMG4 and co. were stranded in the Ocean and Fishy Boopkins offered to take them to land. He was captured by A.S. Swipe but he ultimately escaped.
Since then, he has made appearances on most of SMG4's latest products alongside Bob. He loves hot anime girls, he lives on a beach and was raised by Kermit The Frog and Laa-Laa.
Much sought after in the past, Fishy Boopkins is naturally happy and optimistic, like his first appearance, where he was extremely happy to see humans, albeit by his sensuality. He is shown to enjoy playing with his toys.
However, like Bob, he secretly craves attention and being noticed. This can be seen at the end of SM64: RETARDED RECAP 2016, where it does not explode any end to the name of its favorite brands, before being terminated by SMG4.
Fishy is also implied in being a weeaboo because he keeps a huge collection of Dakimakuras and cardboard cutouts of anime girls and considers them "waifus" (Japanese for wives).
He also mentions that he watches school-themed anime, in High School Mario. He is also a terrible singer, so bad in fact that him singing Bee Gee's "Staying Alive" caused the earth to explode, though this does not happen when he tries rapping in War Of The Fat Italians 2017.
He also eats rocks, it's implemented that he does this because he can not get food the natural way, but it does seem that he does enjoy rocks as seen in SMG4: Mario University, as he eats all the rocks his teacher gives him. In SMG4: Stupid Mario Paint, he is shown to be an amazing painter.
When he is bullied by others he has a tendency to call upon his dad to punish those who are bullying him. However, he chose to get even with Mario himself after he was launched by a slingshot, though his friends assisted him with doing so.
However, he is known to be very stubborn and impulsive when he was eager to help Bob during Rapper Bob concert in SMG4: The Mario Concert, but it ended up destroying and ruining the concert and led Bob betrayed him and ended their friendship.
Horrible Singing: Mostly due to his mouth, Fishy Boopkins is an absolutely horrible singer in every aspect. His singing is so bad that, as shown in DerpTV: Mushroom Kingdom's Got Talent, it can actually cause the apocalypse and destroy the Earth.
Hobo Water Magic: Fishy Boopkins can also give humans the ability to breathe underwater in some way, and is distributed through his hands.
Dad Summoning: Whenever Fishy Boopkins' Dad is around, do NOT make fun of Boopkins, because then his dad will kick your ass! This has been seen in multiple videos. Other times he may be nice to you, such as getting you to places like Didney Worl.
Sonic Waves: In SMG4: The Super Dudes. Fishy Boopkins have the ability to make soundwaves at Wario and his minions.
Durability: Fishy Boopkins was able to survive having his kart launched into the sky when other racers died under similar assaults. He was also able to survive being launched by Mario's slingshot.
Super Waifu Active Smash: In Stupid Mario Tennis Aces, he was able to summon waifu pillows as weapons.
Giant Waifu Summoning: In Stupid Mario Tennis Aces, he was also able to summon a giant Waifu Body Pillow.
Excellent Artistry: While he usually draws low-grade drawings that are usually eye-searing, it's revealed with huge motivation and dedication, as well as having a crayon expansion pack, he can paint high-quality drawings, sometimes able to make perfect imitations of the real deal like the Mona Toadsworth painting. However, this would also cause his arm to be set on fire.
Alcohol Immunity: He has been shown to be unaffected by being submerged in what would be a lethal amount of vodka, though he was not shown drinking it, he was certainly immersed in it.
Unlike most characters in the series who usually speak with subtitles and sound effects, Fishy Boopkins has full voice acting in all his appearances. Presumably if he spoke with subtitles they would be green.
His voice is a parody of Fred Fredburger from The Grim Adventures of Billy & Mandy.
In Hobo Bros, Kevin utilizes his Fishy Boopkins voice when a Spike is on the screen.
In recent episodes, mostly on TheAwesomeMario, Fishy Boopkins has begun to team up with Bob most prominently shown in Boopkins and Bob. However, Bob admitted to using Fishy Boopkins in Super Mario Audition after he accidentally sabotaged his concert.
Despite having a huge dislike for him, SMG4 gave Fishy Boopkins a thumbs-up in Retarded64: Stupid Mario Kart (though this may be due to the presence of his dad). He also invited him to parties a couple times but not Bob, possibly meaning SMG4 hates Fishy Boopkins much less than he does Bob.
He almost succeeded in stealing the Declaration Of Independence. though it hadn't been his intention to steal it.
Fishy Boopkins is apparently a grownup (debunked by himself in SMG4: Mario Preschool) as he said that he did not see land until he was a man. This could just have been a plan to sound like a badass, as he admitted as much.
However, he later says that he is a child in SMG4: Mario Preschool. Keep in mind that this still within the same year. His Mario Kart happens to be a stroller.
Despite being a child, Fishy Boopkins has used profanity, though this is rather rare.
Though he is normally friendly, to steal his Waifu body pillows, or to threaten his anime, is to ask for death.
As of SMG4: Doki Doki Mario Club, Fishy Boopkins now has an Super Mario 64 Mario mod, which is used alongside his Garry's Mod ragdoll in SMG4's more current videos.