Fun accidental mythology parallel in Foxtrot au:
You know how Robert runs afoul of the Dragon Goon (also nicknamed Lóng/Ryuu in fandom) in Sardine, and the guy seems fixated on him?
Well, in East Asian and particularly Korean mythology, Fox spirits (kitsune, huli jing, gumiho/maegu) and Dragons do not get along.
One famous Korean fairytale set-up is "The Monster Fox Threatening a Dragon"; in which the Dragon King of the Western Sea is so injured from a fight with a divine Gumiho, that he seeks the help of a mortal archer named Geotaji/Jakjegeon. The archer helps slay the kaiju fox, rescues the dragon princess, and the Dragon King grants him the princess's hand in marriage as a reward.
It's a little of a subversion of the European trope of "princess held captive by a dragon" cus in this case; the princess is a dragon, and the "dragon/beast" is a hungry fox demon.
There's also Taoist mythos in which foxes work alongside the Celestial Gods against Dragons in times of war. Even in tales where the dragons and celestials are buddies, a fox demon will appear as an opp towards dragons.
Evidently these two groups of animals no likey each other.
This is likely tied to Buddhist symbolism of foxes being symbols of deceit, earth, and femininity, and dragons being royal, airy, and masculine. Sort of a darker version of the contrast presented by Dragon/Phoenix motifs common in mainland asia.
In the Mecha Man Foxtrot au: Robert is a fox spirit hybrid, though he likely doesn't know how deep the Fox vs Dragon grudge goes. The Dragon Guy be glaring at him like he's wearing opposing gang colours.
Which makes the whole thumb-biting and bathroom beat-down seem a little more thematic.
Robert, on the phone: "Grandma, I got into a fight, and I bit a guy's finger off... again." Grandma Su-jin, worried: "Did you swallow it? Was he human? Dear, if he's human you need to make reparations at the temple-" Robert: "No I spat it out. I think he was some kind of dragon hybrid?" Grandma Su-jin: (*loud cackle!*) Robert, confused: "Whats the joke?" Grandma Su-jin: "Just ancient history, dear. Nothing to worry about." :3