He is a friend-turned-enemy of SMG4 who resided at the castle before turning evil after Mario ruined his birthday. He was arrested on his birthday in the blooper "Super Mario 64 Bloopers: Birthday Freakout." and was plotting his revenge to "kill Mario and SMG4 once and for all". He later reappears for revenge in the blooper "Super Mario 64 Bloopers: The Visitor.", which was made a year later once again on his birthday, but seems to get arrested a second time.
He makes a few appearances afterward, with his most recent (and prominent) appearance being in SM64 Christmas 2015 - Christmas Crazies, in which he and the Villager exact bloody vengeance against Mario and the gang, but was later redeemed. Roprinplup14 is now named (on his YouTube Channel) PrinPlup14.
Enzo was once SMG4's friend who made his first appearance in Starman3 Gets 5000 Subs! and went on appear in many other bloopers. In Birthday Freakout, he was celebrating his birthday party with SMG4 trying to keep Mario out. After Mario ruined the party by dancing for 5 seconds and accidentally throwing Steve's lit candle on the carpet (according to SMG4), Enzo becomes extremely angry at the plumber for ruining the best day of his life and hires SMG4's nemesis SMG3 to kill him, but the latter kept failing, much to his frustration.
He eventually decided to have another party to make up for the last one and invites Mario and co. He also threatens to murder anyone who tries to leave. After numerous games, they decided to play Hide 'N' Seek, but Enzo changed the rules so he could brutally murder anyone he finds. He succeeds in finding Mario trying to escape via the basement, but before he could exact his revenge. However, a Policeman burst into the basement from underground and arrested him, while Mario mockingly sang his birthday song. He eventually went to make a few cameos since then.
He reappeared in The Visitor, where he brutally murders the people at the castle and shoves them into toilets. Peach manages to survive being shoved into the toilet but ends up having a mental breakdown from all the torture. Mario, SMG4, and Bowser attempted to catch him but failed. Unfortunately, Enzo was arrested again after SMG4 distracted him with a teddy bear, giving enough time for the police to show up and arrest him.
Afterward, Enzo reformed and became friends with Mario again. At some unknown point, he got reminded of the plumber ruining his birthday and went back to his serial killer ways to the point where the police made a warrant for his arrest. In Christmas Crazies, he learned on TV that Mario and the gang were going on vacation for the holidays, and wanting revenge, he secretly followed them along with the Villager (who wanted to kill Mario for abandoning him on debris).
They managed to crash their plane, but when he was about to kill the gang, the Villager fought him over who should kill the gang first, giving them the advantage to escape. They went to Santa's workshop where they found the gang and tried to kill them again, but Santa used his magic to rehabilitate them. They decided to help Santa prepare for Christmas, but after Bowser accidentally crushed the latter to death with his Koopa Clown Car, Enzo and the Villager went back to their psychotic ways and again tried to kill the gang. Mario managed to stop them by giving them presents, with his present to Enzo being a cake with the words "You're A Psychotic Weirdo". Happy, Enzo apologized to the gang and decide to celebrate Christmas.
Roprinplup14's color code is old: it was made years ago, before the color code generators. Here is it: