Robert Bernard Bowser Junior, usually officially known as "Bowser Junior" but usually simply "Junior", is the most common character in SuperMarioLogan. He is the secondary tritagonist of the series and he is the son of Bowser, but is usually parented by Chef Pee Pee, and his best friends are Joseph and Cody. In his first appearance, Baby Mutant Turtles, he is the main antagonist.
Bowser Junior's personality is extremely variant, and over time has had numerous different sides to him. Over his 4 years of appearing, he has been stupid, manipulative, energetic, immature, naughty, troublesome, selfish, demanding, whiny, bothersome, retarded, and not very smart. He bothers and annoys everyone around the house, especially Chef Pee Pee, and always causes a disruption that usually leads to Bowser yelling at Chef Pee Pee for it. Whenever he asks for something, he usually asks Chef Pee Pee for it. On many occasions, he asks for something very stupid such as in Bowser Junior's Midnight Snack when he asks Chef Pee Pee to buy him a snack at the gas station even though there is a mountain of snacks to eat at the house. He is also a somewhat picky eater as shown in many episodes. He is also a spoiled brat because in Bowser Junior's Summer Vacation, he demanded Chef Pee Pee to buy him all the trains but he only got two from the store. Junior loves his Thomas toy a lot, so he gets very sad if he loses it as shown in "Bowser Junior Loses Thomas", like his dad did with Charleyyy in Bowser's Depression. Much to his loud crying, which annoys Bowser, Bowser beats him up. He also gets rabies and starts acting weird in Bowser Junior Gets Rabies!. When the squrriel bit him, he turned into a wild animal and was foaming at the mouth. Chef Pee Pee gave him a pill and that made Junior feel better and then he bit him. At the end of the video, Bowser Junior said that "Chef Pee Pee was having "babies" himself.
One of the most notable things about Junior is how he has changed over time. In his first appearances in 2013-2014 when he was only 5 years old, Junior was a spoiled brat who portrayed a general child that age. Over the next few years, Junior started to become smarter, but still was stupid sometimes when he was with Joseph and Cody. Since Bowser Junior has turned 8, he has been quite a bit more mature. One notable video with this was "The Baby Project" where Junior was strongly encouraged to do as good as possible and fighting the retartedness of Jeffy. It is a very unique aspect how Junior is growing over time.
It's pretty apparent that Junior has some serious mental instability (or it is typical for a child his age), if anything happens that may affect him badly, or something doesn't go his way, he will react in very unhinged and insane episodes. As seen in Bowser Junior's Punishment! Junior was placed in the corner for 5 minutes and he was acting all weird, and in Bowser Junior Loses Thomas! he lost Thomas and was sad all day. In Bowser Junior Needs Glasses! Junior wore glasses and his friends mad fun of him so he read a medical book and got smarter and thinks he's smarter than everyone. In Bowser Junior's Flu Shot! Junior was scarred after he got his flu shot and was on a wheelchair and wore a cast on his leg where he got his flu shot and claims to have been "shot" by the Brooklyn guy. And in Bowser Junior's Cookies! He left a sticky note which had cookies written on the fridge and was hoping for Chef Pee Pee to get him cookies but Chef Pee Pee said that he didn't see it and Junior kept repeating he didn't see it and placed sticky notes all over the house and the car.
On rare occasions, he is found to be pracially rejudice to black people. This is evident in Black Yoshi's Job (Black Yoshi is asked to babysit Junior while Bowser and Chef Pee Pee go to the hospital) when Junior is surprised to see Black Yoshi walk up to him while he is playing with his dinosaurs. Junior cries, "Oh my god! Black Guy! Don't take my money! Protect me, dinosaurs!" Black Yoshi then asks, "Why is everyone in this house racist?" There is another occasion in Bowser Junior's 6th Birthday after he opens the door to let Cody and his family inside, not expecting Cody to have a black step-father. After greeting Cody, he exclaims, "Cody's mom! Look out there's a black guy behind you!"
Junior is also known for sharing false stories. For example, in Bowser Junior's Flu Shot!, He explains to Joseph and Cody that a guy came in with a gun, shot Bowser and Chef Pee Pee, and getting shot in the knee. Also, in No Crust!, he explains to the Brooklyn Guy that Chef Pee Pee used a chainsaw to "kill" his sandwich, in reality, all he did was cut the crust.
However, despite all of this, even Junior is capable of genuine kindness. The shining example of this is when he felt bad for Chef Pee Pee's suffering on his birthday, and as an apology, threw a surprise birthday party for him, with Joseph and Cody's help. He even apologizes for treating Chef Peepee badly for the entire time they've known each other (although, thanks to the new status quo, this is rendered redundant via negative continuity).
Despite being a generally dumb character, he has shown to act smart on some occasions such as Bowser Junior's 1st Grade! Part 5 where he states that blue stars are hotter than red stars, in Cool Cody! where Bowser Junior figures out how to change Cody back to normal, in Bowser Junior's Bad Luck! he states that superstitions are not real and that all the bad luck he was getting were coincidences, in Bowser Junior's Piggy Bank! he knows how to stop his dad from getting arrested without getting himself in trouble and in Broken where he has the idea to put the one-piece tuxedo on Ken and give it to Cody so he stops crying. Along with Joseph, Bowser Junior keeps trying to prove to Cody that Ken is a doll and that the Sun is a planet.
He doesn't act much bratty anymore, as he improved from military school. He's also simply grown up in the past few years, as he was just 4 in his first modern appearance, but 8 now.
Bowser Junior always annoys Chef Pee Pee with his stupid requests, making Chef Pee Pee hate him. Because of this, sometimes when Junior is about to do something that could be dangerous in some way, Chef Pee Pee hopes he kills himself in the process, but sadly for Chef Pee Pee, this never happens. He also annoys him by asking to play toys with him.
Bowser Junior usually interrupts his dad while he watches Charleyyy and Friends. Bowser usually likes his son, but he hates when he annoys him. He basically annoys him a lot and sometimes it leads to Bowser beating up his own son then sending him to time out. Despite this, he gets along with his dad okay and loves his dad very much and strives to be like him.
Bowser Junior and Joseph (With his last name being "His friend from school") are friends that mostly meet at school or at Junior's home to play toys. What often happens is, if somebody is cooler that Junior, Joseph is on their side rather than on Junior's side.
Bowser Junior and Cody get along pretty well with each other. Like Joseph, he invites Cody to his house regularly. There are times when Bowser Junior is really mean and harsh to Cody. Cody keeps trying to tell him the truth about things (like the Sun being a star, Pluto no longer being a planet or the Earth being round), but Junior's nonsensical logic and denial makes it hard for Cody to reason with him.
Bowser Junior usually hangs out with Toad. They are very good friends, although Toad usually gets Junior in trouble, such as in April Fools!
Bowser Junior met Jeffy in Bowser Junior's Game Night 3 and have shared a good relationship ever since. In recent videos, the two have played together more and usually have fun doing stupid stuff together.
In Jeffy Loses His Teeth! he caused Jeffy to lose his teeth by using Jeffy's mouth as a tee for playing T-Ball and hitting him with the bat.
Youtuber Kushowa says Junior has a bad influence on Jeffy.
Bowser Junior first met Rosalina in Jeffy's Birthday! when he and his friends were about to go on the SkyTubes at Chuck E. Cheese's with Jeffy, and found her to be really hot.
In Smart Jeffy, Junior caught Rosalina's attention by calling her "Busty Tits" and told her that Jeffy had an accident on the trampoline that was in his playroom.
But it's unknown if these two characters share a good relationship or not.
Junior's reception has changed a lot since becoming a main character. He has arguably the most polarized reception of any SML character ever. Since becoming a main character, SML fans will almost think extremely positively, or extremely negatively, of the character. Bowser Junior was once hated by a majority of viewers, but it recent times, he has become more likable by more people, especially since the introduction of Jeffy. It is mostly classic SML fans of older videos that hate Junior, while newer fans react more positively to him.
Bowser Junior's negative reception has been due to the character acting like a brat, being retarded, rude to his friends, or even because of making racist jokes about bad things. He is also hated because Logan has been overusing him, and has no new material to go on. Other reasons for Junior being hated include his annoying voice and how much he tortures Chef Pee Pee and Cody for no good reasons.
The character has, however, seen an increase in positive reception over the years, mainly due to an improvement of the character himself as well as becoming gradually less annoying. The character is partly responsible for SuperMarioLogan's subscriber count skyrocketing, as it began to do so when Junior videos became more common, and now he doubles his sub count every year. Junior videos also get more views than most other videos and some of the most views on SuperMarioLogan.
Unfortunately, Junior's reception started to decline once again after his appearance in Bowser Junior's Package!, when he tortures everyone because he thought that they stole his package. This angered a majority of fans and has also gained quite a bit of controversy in the SML community.
Bowser Junior's gamer tag is "GetRektFgtLol", but it was reported because he kept ruthlessly insulting everyone, especially Black Yoshi.
Bowser Junior has burned down more buildings than any other character in the series with 2, including the original house, and his first-grade school.
Bowser Junior has had more birthday episodes than any other character in the series with 4. He's also had the most highlight for aging, showing his birth in Mario and Luigi's Stupid and Dumb Adventures, and bringing him back at 4 years old, and now is 8 years old.
One time, Bowser Junior locked himself in his closet for a week straight.
In a Dabhdude live stream, Logan stated that the reason Junior is in so many videos is because it's hard to think of ideas for the other characters.
He says "EVUR" instead of "EVER" sometimes.
He had a Wii U before the house fire.
His favorite song is "All Star" by Smash Mouth.
The reason why he got sent to military school is because he got into Bowser's clown car and broke the glass table in the video Bowser Junior's Clown Car!, and also in the video, Cody's Revenge!, he got blackmailed for throwing a temper tantrum after losing a game of Chess, throwing a Ken doll, breaking a bowl of Raisin Bran, getting forced to watch Big Hero 6, screaming and behaving badly, and breaking a jar that was in tribute to Mittens.
His theme song is "Get Outside" by Jason Farnham. 
He does hate Big Hero 6, Because he is voiced by Logan Thirtyacre, and Logan does hate Big Hero 6. Bowser Junior and Mario are personas of Logan, and often portray his character through these characters.
His favorite number could possibly be seven, due to him thinking there were 7 pins in Truth or Dare, He claims that he can stay up until 7 AM in Bowser Junior's All Nighter, and there are 7 parts of the Bowser Junior's Summer School series. And when he asked for Chef Pee Pee to make food, he said to pick one meal most of the time he'll say "How bout' seven?"
Bowser Junior has celebrated his 8th birthday! Which birthday episode is your favorite?