In "Gift of the Card", we're introduced to Rasticore, a seemingly more dangerous and powerful villain than most of the others Star and Marco have faced. He also happens to be another lizardman just like Toffee and apparently had access to the same technology as Toffeenote Toffee used a handheld tracking device to find Star's wand in "Macro Grows a Beard" while Rasticore uses an identical device to track Star and Marco across dimensions in "Gift of the Card". so there was definitely potential for him to be linked somehow to the first season's Big Bad. However, instead of the Knight of Cerebus and/or potential associate to Toffee one thought he should have been, Rasticore doesn't even get to fight Star and Marco. Instead, as soon as he finally finds the two, he gets disintegrated by the Quest Buy gift card in a matter of seconds. He takes until season 3 to come back to his former glory, but only for one episode before being reduced to an arm again. Season 4 shows that he is working at the Assassin's Guild, as a dishwasher, and is in no way connected to any of the show's conflicts, making people feel that where they could have gotten a really cool villain, they got nothing.
Despite being introduced as Marco's love interest in the first season, Jackie was utilized very little in the series, even after she and Marco began dating, with little exploration of her character outside of being a level-headed skater girl. This was made worse when Jackie broke up with Marco early in season three, despite only being a couple for ten episodes (and of those ten, their relationship isn't even mentioned in passing for most of them), after which she disappears from the show outside two brief appearances in the final season.
Lekmet, the goat demon of the Magic High Commission. Unlike the other members of the MHC, he never gets A Day in the Limelight during Season 2 (which means that he also never gets to interact with either of the show's protagonists), and in the season's final episode, he pulls a Heroic Sacrifice in order to save Queen Moon and the rest of the Commission from the Toffee-possessed Ludo. This is a waste because the Commission ends up being even more relevant in seasons 3 and 4 , what with them being behind the conspiracy surrounding Eclipsa, her daughter and the Butterfly family. As the MHC's chairman, it would've been interesting to know what Lekmet's perspective and role on all this was, but alas he's too dead to share anything.
Tom was somewhat underutilized as Star's boyfriend. At the beginning of Season 3, it initially looked like another love triangle. Season 3 was about mending the historical racism between the monsters and mewmans, Tom and Star's relationship wasn't exemplified as a functional, interracial relationship until the second half of season 3, where it was mentioned offhandedly in the ending of "Is Another Mystery". Tom was eventually put to use in the second half of the season but still could have been utilized much earlier.
Season 2's episode Into the Wand marked the first appearances of the many queens to come before Star and Moon, particularly drawing focus (for both Star and the audience) on Eclipsa, Solaria, and Celena. Of the three however, only Eclipsa really ends up mattering to the plot, being the one to further the Myth Arc.
Solaria does serve as the motivation behind Season 4's Big BadMina Loveberry, but outside of that, contributes little to the plot. Her relationship to Eclipsa, namely that she's Eclipsa's mother, doesn't even come into the series until its close to its conclusion, and serves more as a footnote.
Celena serves little to the plot outside of being a queen. Her epitaph and tapestry makes a big deal about her hiding behind her wand, and her entry in The Magic Book of Spells mentions she is half-demon like Tom, making Star part demon.note 1/32nd to be exact The attention drawn to her, combined with said heritage had potential for interesting developments in the plot, and for interesting parallels between Star and Tom due to similar heritage being revealed. However, by the series end, Celena is simply another queen amidst the many others, her demon heritage not even being mentioned In-Universe.
The Magic Book of Spells introduced Seth, the leader of the Septarians as well as Toffee's boss. It was under him that Toffee killed Moon's mother Comet, and he was described as a foil to Mina, being a monster that detests Mewmans to the point of wanting nothing less than their complete and total genocide. He was described in a manner befitting that of a Greater-Scope Villain, especially with Toffee's line before his death, proclaiming additional plans and knowing how things would turn out. Despite this though, he is entirely absent from the series outside of the book itself, not even getting referenced, and the final antagonist role is instead given to Mina. It was made even more confusing when, within minutes of each other, producer Dominic Bisignano and creator Daron Nefcy gave contradictory statements on the character when asked by a fan on Reddit. The former stated that he's still alive and, if the show was ever revived for another season, could play a major role. However, according to Nefcy, Seth had been dead for some time now. If we take Nefcy's word as the final say on the matter, this means that a major character not only never appeared in the series proper, but has also been dead the entire time, and none of this was revealed until the series had already concluded. Which to some felt like a dick move after fans were irritated nothing came of him and wondering where he was.
After Toffee’s defeat at the beginning of Season 3, Ludo starts to become Out of Focus, appearing in very few episodes from that point on. This made his redemption feel very forced and poorly thought out, especially since it introduces Ludo’s brother, Dennis, who is a genuinely interesting and likable character of whom many fans would have loved to see more. The fourth season completely excludes Ludo, his army, and his siblings from the overall plot. A few episodes in, he gets back his army and castle and swears to be a better person. His only appearance afterwards was for ten seconds in the finale playing basketball with Dennis and inviting Star to join.
River's only involvement in the series finale is trying to get an injured Globgor to the magic temple. He never finds out about Moon's betrayal and support of Mina. It would be interesting to see what his reaction would be like.
Globgor. He serves as the big motivation behind Eclipsa's actions in Season 4, however, he ends up only being the focus of 2 episodes before being mostly sidelined. In the final episodes, he is quickly taken out of commission and soon left in a comatose state, preventing him from contributing more. Finally, while he is thankfully shown to be okay in the finale, he doesn't get a single line of dialogue, leaving some feeling he was wasted.
Reynaldo the Bald Pate. The Magic book of Spells both introduced him and revealed that he used to be a member of the Magic High Commission until he was kicked out due to being cursed by Rhina the Riddled. Despite being a member when the Meteora-Festivia swap happened and the potential for a revenge subplot against the remaining MHC, he only ever appeared in one episode in Season 4 and was never seen nor mentioned again.
Mina Loveberry is an interesting case, since the problem isn’t that she was underutilized, but rather, that she was used at the wrong place at the wrong time. She ends up being the final villain of the show, which many fans can agree doesn’t work for the kind of character that she is. Mina is nothing more than a Psychopathic Manchild who’s obsessed with destroying monsters in any way that she can. She would have worked much better as a recurring villain akin to Ludo, with her potentially even teaming up with Star to defeat a different Big Bad for the finale. She also had the potential of being a compelling Tragic Villain, since she used to be a shy lowly peasant girl whose personality was altered when she was turned into a Solarian, and she's both The Last Of Her Kind and turning insane because of the magic infused in her. However, many of the information about the Solarians are All There in the Manual.
Eclipsa Butterfly was heavily featured in the Season 3 trailers. However, she rarely appears in the first half. Thankfully she becomes more prominent in Season 4, but it would've been better if she played a bigger role more often in the majority of Season 3.
