Bowser Jr.

"I will make Papa proud this time, by finishing you off myself!"

Bowser Jr. is a boss character in Prismverse Saga. He makes an appearance in some of the episodes, mainly staying by Bowser's side. Whenever Bowser is not the main villain of an episode, Bowser Jr. usually helps his father in whatever he needs, as much as possible. Voice actor is Caety Sagoian.

History
Bowser Jr. first appeared in Super Mario Sunshine, by using a magic paintbrush that he stole from a man in white coat, he donned a disguise, looking like Mario, he had terrorized the denizens of Isle Delfino, and infected most of the island using ink. He revealed himself after Mario defeats Mecha Bowser in Pinna Park, thinking Princess Peach is his missing mother and Mario is the one who kidnapped her, and also telling that he's Bowser's son. After the final battle, Bowser Jr. tells his father that when he grows up, he wants to defeat Mario by himself, making his father proud.

Ever since then, Bowser Jr. has been on his father's side, helping him to defeat Mario, albeit failing miserably in the end. He also makes appearances in spin-off series, whether as a villain or not.

In Prismverse Saga
Bowser Jr. first appears in SMATSP, as the mid-boss of Volcanic Lavalands. He teams up with his siblings to attempt defeating Mario Bros, but they fail in the end. After Bowser's defeat, Bowser Jr. stays in his castle with the Koopalings, to protect their home when their father isn't around. In the credits, He comes along with Bowser when he makes the truce.

In the episodes where Bowser isn't the main villain, Bowser Jr. usually helped his father in certain chores, to make him feel better. But whenever Bowser decides to make an evil scheme, he always follows him to the end, as he aims to be as strong as his father one day.

Boss Battle
(WIP)

Trivia

 * The music that plays during his and the Koopalings' battle is a remix of the Boss Battle theme from Super Mario Bros. 3, remixed for Super Smash Bros. Ultimate.
 * He fights alongside the Koopalings, making their battle the only boss battle with tag team in SMATSP.

Lore
Bowser Jr. is the son of Bowser, and the next heir to Koopa Clan's throne. He was born 10 years after Bowser's first defeat, with his mother being missing after his birth. Bowser Jr. grew with his father, as Bowser worked on his evil schemes, Bowser also spent time with him, teaching him the ways to become an evil Koopa. As the young Koopaling was inspired from his father's attempts, but he was feeling sad as his father's plans always backfired by the works of two plumber bros.

When Bowser Jr. turned 8 years old, Bowser thought it was time to make him a part of his schemes. The young Koopaling stole a magic paintbrush from a man in white coat, and was sent to Isle Delfino, after learning that Mario and Princess Peach will go there for a vacation. Bowser Jr. had caused a great ruckus on the island, as he donned a disguise that looked like Mario, to make him the criminal when he arrived. His plan worked, as Mario was under custody and he had to clean the ink splattered by Bowser Jr, the young koopaling had the chance to kidnap Peach, which Mario prevented a bunch of times, but until he succeed at the end, and took her to Corona Mountain, where Mario faced him and his father, and defeated both in the end.

After his first defeat, Bowser Jr. didn't give up and wanted to defeat Mario. He managed to kidnap Peach after hiring a Lakitu who possesses thunderous powers to distract Mario. After his father was melted in the lava, he gathered his skeletal remains and revived his father for another dual battle, only to be defeated yet again.

And since then, Bowser Jr. works with his father and his siblings to finally get a chance to defeat Mario and Luigi once and for all, mainly partaking in small invasions from airships or tank forces he commands in certain places. But from his ambition, it's obvious that he'll grow to be the Koopa King just like his father is someday.