Tom Lucitor to Meteora Butterfly, as they both represent the opposite options of society and family accepting a half-monster hybrid, especially those born into royalty. Where as Meteora is the daughter of a Mewman with a monster, a group of poor creatures that is hated by society, she suffers from it and has the throne taken from her. Tom on the other hand is largely beloved, if still suffering from Fantastic Racism in minor ways among Mewmans, he's still a royal who is the son of a Mewman with a demon that grants him a palace and the right to eventually govern the underworld.
The series highlights Marco Diaz and Star Butterfly different reactions to the thought of having feelings for the other: While Star's feelings have been building up the more she was drilled despite saying otherwise, Marco remained indifferent to the possibility, not thinking anything would come of it. When it came to Star admitting she has a crush on Marco; Star attempts to avoid acting on it further, while Marco moves on and doesn't make a big deal about it... for a time.
Globgor serves as one to Wrathmelior, the mother of Tom. They're both massive, red-skinned, horned demon-like entities with multiple eyes, with weird names compared to their spouse and children's relatively more normal names, who fell in love with a Mewman and gave birth to a Mewman-Monster hybrid. Unlike Wrathmelior, however, Globgor had his wife and child taken away from him, and he wound up being crystallized and imprisoned inside his Monster temple.
Archibald to Manfred. Both of them serve as the main butler figures to their respective Queens. But while Manfred was a Mewman who was a snobby racist, Archibald is a monster and is a pleasant fellow in comparison.
Hornanne Pony Head to Chezna Pony Head who willingly had her horn filed off.
The Lucitors contrast Eclipsa's monster family. Eclipsa's a Mewman mother, while Dave is a Mewman father, with their larger monster spouses being of opposing genders. The Lucitors also got to keep their hybrid child, which had great importance in influencing how Tom developed as he grew up.
Wrathmelior serves as one to Globgor, the father of Meteora/Mrs. Heinous. They're both massive, red-skinned, horned demon-like entities with multiple eyes, with weird names compared to their spouse and children's relatively more normal names, who fell in love with a Mewman and gave birth to a Mewman-Monster hybrid. Unlike Globgor, however, Wrathmelior not only managed to keep her child, but also gained a political ally in the Butterfly royal family.
Wrathmelior also serves as a foil to John Roachley, Rhina the Riddled's husband and Celena the Shy's father. While they both fathered Mewman hybrids, John was such an abusive husband that Rhina had to use a heartbreak spell to try fix things, only to end up killing him, while Wrathmelior is a legitimately nice woman who won Dave's heart and had a loving relationship with him.
King Shastacan to Globgor. Both were the husbands of Eclipsa, but Globgor was her childhood friend and second husband while Shastacan was betrothed to Eclipsa. Shastacan was shorter than Eclipsa, while Globgor is absolutely enormous. The Mewman king always had a serious expression on his face while Globgor had a noticeable smile (which caught Eclipsa's attention). Shastacan is dressed in a blue and white royal garb, whereas Globgor is a red-skinned shirtless monster wearing only a black speedo for an outfit. Shastacan abhorred Meteora and considered her heinous, while Globgor loved his daughter, and was crystallized while probably fighting to protect her and Eclipsa. Also, while Eclipsa had an Awful Wedded Life with Shastacan but she was Happily Married to Globgor.
Baby to Glossaryck. She is more stern and strict when assessing Star's magic and skills, but more honest and direct in her training.
The Butterfly parents to the Diaz parents. Both sets of parents are the parents of the two main protagonists, the Diazes are from Earth and the Butterflys are from Mewni. While the former are more laid-back and open-minded, the latter are stricter and stiffer. As an added bonus, the Diazes wear warm color clothing, while the Butterflys wear cool color clothing. The Diazes also have two children as of "Marco Jr.", while the Butterflys only have one child.
On the surface, Festivia and Moon couldn't be any more different what with their attire and surface attributes, but they both used their wands to fight in horrible wars that threatened to destroy their kingdom, put on facades of strength and confidence to make their subjects feel secure, and possess similar Facial Markings.
Celena Butterfly to Tom Lucitor, another hybrid with a Lucitor parent.
Celena is the picture of regal beauty and grace in Mewni, wearing long robes, having long hair, and being so beautiful that she could disarm monsters with a glance. Despite being royalty, the short-haired Tom usually dresses like a punk rocker and often acts like a Royal Brat with anger issues and the need to control others (pre-Character Development, that is).
Celena was born from a loveless, abusive marriage between her Mewman mother and Lucitor father, the latter who was accidentally murdered by a heartbreak spell before his daughter was born. Tom's parents are presumed to be Happily Married, with a Mewman father and Lucitor mother.
Celena dealt with her problems and insecurities by withdrawing into herself, ironically attracting more people who wanted to hear her secrets. Tom drove almost everyone away with his Hair-Trigger Temper despite not wanting to turn out like his similarly-tempered father, until he went through Character Development with some help.
Eclipsa to Moon. Eclipsa is a carefree woman who is always calm and joyful despite what happens around her; her advices to Star tend to surround the theme of doing what's best for her, focusing on self-discovery and self-empowerment; she also believes that all knowledge is good knowledge, which prompts her to meddle with dark magic; she was known to empathize with monsters and even fell in love with one. Moon carries herself sternly and proudly; while advising Star, her focus is in self-improvement so Star can become the best queen possible; she tends to keep things hidden from others when she notices it might cause trouble and has loathed the dark magic chapter of the spell book Eclipsa wrote; she also harbors the same Fantastic Racism as the rest of her family also share. In regards to being a mother, Eclipsa was unable to be there for her daughter's (Miss Heinous/Meteora) life, while Moon has always been there for Star's.
Their differences are highlighted again in season 4 with Eclipsa, now as Queen, improving to be a better one and doing selfless actions at the cost of her own happiness. On the other hand, Moon is content to live a quiet life in the yurt village with River, but plans a coup against Eclipsa out of anger for the latter accidentally sending her to the Realm of Magic, thus putting her own feelings ahead of others' safety.
Eclipsa to her mother Solaria, who in many ways was her opposite. While Solaria was fanatical in her hatred of monsters, Eclipsa understood and related with monsters more than she did with mewmans, even to the point of marrying and having a child with a monster. While Solaria preferred to rule alone, only taking a lover to secure an heir, Eclipsa loved Globgor and hoped their relationship would change Mewni for the better. While Solaria was influential enough to reignite anti-monster bigotry in mewmans that lasted for over 300 years, Eclipsa has a 0% Approval Rating among the mewmans of Mewni but is generally well-liked by the monsters. Solaria was a butch Action Girl who's wand took the form of a Laser Blade that exuded light, Eclipsa is more of a Lady of War who's wand is a parasol that blocked sunlight and reflected her affinity for The Dark Arts. Even their names are total opposites to one another; Solaria's name evoking the sun, Eclipsa's evoking an eclipse, or the blocking of the sun.
Past-life Meteora was taken from her parents, unjustly stripped of her throne, raised by an abusive robotic mother who "taught" to be ashamed of her origins, and grew up to be an uncaring, crazy woman; Current-life Meteora can be properly raised by her loving parents who never teach her to repress her true nature, is given back the throne via Star, and shows that while she may be a Creepy Child with an Irrational Hatred toward Marco, she is capable of showing concern for others.
Like Toffee, Rasticore a Septarian who acts with blatant disregard of the Mewman/Monster Accord for his own personal gain. Unlike Toffee, he's brightly colored, relies on technology rather than magic, possesses a hulking physique, is barely dressed, has an incredibly long and intimidating name, growls all of his lines, and is a bonafide hired gun rather than a master manipulator posing as one. To hammer the point home, they're both struck down by devastating magic attacks.
Saint Olga to Eclipsa. Both were mother figures to Meteora Butterfly. Eclipsa was Meteora's biological mother who was a genuinely caring parent who adored her daughter's monster features but was forcibly separated from her child, Saint Olga was Meteora's adoptive, abusive mother who emotionally manipulated Meteora to hide her monstrous nature and "raised" Meteora all of her life. Also, while Meteora loved Eclipsa and never hurt her, she killed Saint Olga when the android made one too many inappropriate comments.
Despite being an Affectionate Parody of the main protagonist, Quasar has several differences compared to Star.
While Star's appearance and background is based on Fairytale Motifs and fantasy, Quasar's theme is centered around Science Fantasy.
While Star wears devil horns, Quasar wears a helmet with angel wings.
Quasar is also shown to practice the already existing spells for her bell rather then coming up with creative/on-the-spot spells like Star.
She also seems to have a positive relationship with Indexia which contrasts Star's complicated and frustrating relationship with Glossaryck.
