Corey and Trina are siblings. They both hate each other and get into sibling rivalries a lot. Trina always goes out of her way to be completely mean to Corey. She hates Corey so much she would go to the point of rage. Corey on the other hand doesn't directly do anything cruel to Trina. He decided to express his hatred toward her by subtly pestering her. For instance: When he does this, he always starts off small and then makes it so that the things he do get more and more annoying to the point where she freaks out and goes into diary mode. He also tries jokingly being "nice" to her or sarcastically treating her like a friend. Trina is always the one who starts their fights; however, Corey is always the one who gets the last laugh.
Trina came out of the car and she had to drive Corey and his band to the Carnival Derby. She was not happy about this and so she acted bossy toward Corey, Kin, Kon, and Laney and immediately told them the rules of being in her car. One of them was "No singing" which she said when she pointed at Corey. On the ride to the Carnival Derby, Corey told Kon to distract Trina which he did in a annoying way while Corey stole her diary from her purse and read through all her secrets. He then got the idea to just annoy her until she went into diary mode. At the derby, Corey did many annoying things to Trina, like messing up the ride for her and making her barf on everyone. He also got Kin and Kon to mess up the roller coaster for her. He entered Pinktastic into the Smash Up Derby and this made Trina get mad. Finally, he made her go into diary mode when he made her figure out that she was going up against Nick Mallory in the race. He then stole the diary from her, got the lyrics, and played a song and everyone cheered for Grojband while Trina's time at the Carnival Derby with Nick was ruined.
When Trina heard about Corey's Chicken Pox Party, she called Mayor Mellow and had it quarantined in a bubble where she locked anti-scratch mitts on everyone to ruin it. Corey made Trina go into diary mode as usual. However, this time, he made her go into a love diary mode. Corey set up a game of spin the bottle between Trina and Nick and then Trina and Nick started to kiss. Whereas Trina kissed Nick on the ear, thinking that it was on his lips. This made Trina so happy, that we went into love diary mode. Despite Corey's hatred toward Trina, Corey still seemed to be perfectly fine and supportive of making Trina happy. However, in the process he also managed to give Trina the chicken pox. While Grojband was singing, Trina was no longer happy as she was seen grimacing at them and scratching her pox.
After overhearing Kin's warning to Corey that he shouldn't press the evil button on the back of the Auto Toned helmet, Trina sees this as an opportunity to sabotage the band, she snuck up behind him, grabbed a disco ball, lowered herself within range, and pressed it, causing the helmet to go rogue. Later in the episode, Corey planned on intentionally making Trina win the raffle, making her so happy that she would go into love diary mode.
Corey and the rest of the band, mutated Trina's plant with their music. This made Trina very angry at them. However, when she found out about this, she was forced to help Corey because that would be the only way to save her plant. Grojband ended up stopping Planty by making salad out of him. Trina was so enraged to see them ruin her science project. Corey sarcastically told her that there was no harm in doing so because that would simply mean that she would be held back a grade and put in the same grade as himself where he's popular. The thoughts of being in the same class as Corey terrified Trina and made her go straight into diary mode.
When Trina sees Grojband dressed in bear costumes, she immediately reports them to Mayor Mellow, who extradites them to Peaceville Zoo. Corey gets revenge on Trina by convincing Nick to gather all of the guests for her party to come to the zoo instead
Grojband resort to hooking Trina up to a machine to make her forcibly watch their video and write lyrics, but their video is so disturbing it causes Trina to go into shock. Unable to wake her, Corey and the gang are forced to journey into Trina's dream to rescue her.
This episode hints that many years prior to the series, Trina may have had quite a different relationship with her younger brother. When Grojband enter Trina's mind they discover an much nicer, alternate version of Trina, who goes by the name of Katrina (which is Trina's real name). Katrina is the exact opposite of Trina, being kind, cheerful, obedient, and loves her little brother dearly. Corey speculated that Trina somehow locked her trap the nicer side of herself in her own mind. Katrina helped Corey and Grojband escape from Mirage Band, and brought them to her dungeon where she is delighted to see Corey. Katrina gives Corey a "bubble hug" where she blew into his belly button, tickling him and making his laugh. Corey proved to have been embarrassed by this as his friends all laughed at him.The Justice Band, however after a series of incidents they get mistaken for real superheroes. Trina is unable to tolerate this and is determined to reveal them as frauds, after a few attempts backfiring, she resorts to dressing up as Justice Band's arch-nemesis Stiletto and goes shame them. She attempts to show Justice Band failing to save Mina who is peril, and bring their image down. However when this fails she accidentally puts herself in danger and instead settles on Justice Band failing to save her.
When Trina sees that the band was using a time machine to travel one year in the future, she took out Corey's guitar and smashed a hole in the machine so that it would hopefully kill them or at the very least, keep them trapped in the future forever. In the future, Trina is implanted with the Blab Tap and enslaves the entire town, Corey knows the only way to break everyone free of her hive mind is to destroy it with the one thing she hates the most: Their music. First of all, they needed Trina to go into Diary Mode to get lyrics. Instead of the usual anger, Corey made Trina go into a Love Diary Mode where he hooked Nick up to the same system as her. The only reason Corey did this was so that he could overthrow her. Corey and the band played the song You're Going Down, which Trina survived by blocking the sound out with a noise cancellation upgrade in her Blab Tap. He then tries to get the song into the Blab Tap network, by hooking himself up despite the fact that he's risking his life by doing do. However, Mina beats him to it and the music in her memory passes into Trina's mind and causes her to break the connection.
At the beginning of the episode Trina snatches Corey's Guitar and throws it into a woodchipper, resulting in it getting shredded. Corey is exasperated, but at the same time is confused as to where the woodchipper came from.
Trina showed a montage of images where she's made members of Grojband feel unhappy. A picture of Trina with chainsaw about to chainsaw Corey's guitar in half was seen. Corey was seen running toward her, trying to stop her with a terrified look on his face. This is implied to have been something bad Trina has done whereas she's actually succeeded in making Corey feel unhappy. When Trina was under the control of the mind controlling bracelets, her hatred for Corey was still strong enough for her to happily mention her hatred for him. She did things such as saying "Hey, look everyone. It's Corey the loser!". She also intentionally tried to anger Corey by making The Newmans play a concert there. When Corey was under the control of the bracelet, he was happy enough to like Trina and not get annoyed by anything she did. When Corey broke free from the bracelet, he made Trina know that everyone loved him as much as they liked her. This made Trina get so furious, that she went completely insane and she broke her bracelet off and so she went into yet another one of her diary modes.
At the bubble festival, Trina sees that Corey is present and plots to get rid of him as she thought he would ruin her time. She shakes up a bottle of pop (with Mina's help) and places it where Corey can get to it, then sits back and watches the outcome. Later on when Corey and the gang need to restore the festival and get lyrics from Trina, he has Grojband bring Trina about the manhole so that she could be sprayed with pop.
When Trina manages to beat Corey in a gig involving playing guitar video game, this causes Corey to become depressed and go into withdrawal. He develops an obsession for the game and beating Trina. Later on he discovers out Trina composed a song, which has become the biggest hit ever. The fact that she was living his dream, and that the song was almost entirely comprised of her diminutive word "Nick", proves too much to Corey, and he finally snaps. His anger is so intense that when Laney tells him to breathe he exclaims "I've been breathing my whole life, and it's got me nothing!" but what drives him the most insane is that Trina's song didn't even traversal lyrics.
For most of the episode Trina refuses to believe the rumors started by Grojband about the end of the world. However Corey needs her to believe it in order to obtain lyrics to stop the carnage inn the town. So Corey convinces Nick that the world is ending, and has him convey the message to her. After they obtain their lyrics, Grojband sings If the world is ending, during which Corey points Trina in the direction of Nick, and encourages her to "ask someone for a dance", to which she needs his advice.
Trina teams up with G'ORB to defeat Grojband and destroy the world, so that she can be with Nick Mallory. Corey discovers that Trina had gotten rid of their instruments so they couldn't play, he concedes defeat and says "You win Trina".
- It's possible that the names of these two are a reference to Corey and Trina, given that they were musicians and that they were brother and sister.