So this isn’t a random headcanon or even fan theory, but I kinda like the idea that Toffee is/was Queen Eclipsa’s son. Like I know, it’s random and any supporting evidence for it is circumstantial at best, but hear me out.
First there’s Toffee’s design. And maybe this trait is just a defining feature so the audience can recognize him easily as an important character, but it still kind of bugs me. What am I referirng to? Toffee has hair. Actual hair. In comparison, other reptilian monsters we’ve seen in Star VS The Forces of Evil don’t have hair. They may have features that are meant to represent the idea of hair, but they all still look like they belong on a reptilian creature. More like frills or elongated scales. Yet here’s Toffee with this well styled, mammalian trait. But maybe the creators are just taking creative liberties. I can buy that.
But then, Toffee is biologically immortal and in both the present and in Moon’s flashback is shown as an adult. And no one ever mentions how long Toffee has been around. So it’s very possible he’s centuries old and just hasn’t drawn as much attention to himself has he has in the show.
And finally, Toffee is incredibly powerful when it comes to magic. I’m not just referring to defeating the high commission either, although that is a good example. But another hint we were given earlier in the show was in Storm the Castle, when Marco tries to punch Toffee. We as the audience clearly see Toffee standing right in front of Marco, but as soon as Marco throws that punch Toffee is gone, Marco bruising his hand against the crystal cage and Toffee standing behind him. If this was meant to be a joke alone, why make the transition between real Toffee and reflected Toffee so noticeable? But again, I could be reading too much into that. Another good example also comes from Storm the Castle; Toffee knows about the Whispering Spell and what exactly it does. He could have picked up that knowledge from years of research (take a look at the book he’s reading in Mewnipendence Day), but how did he know that it was traditionally the first spell taught to the princess? Because his mother taught him. Eclipsa might have been around long enough for Toffee to start learning magic from her before she was crystallized.
And let’s not forget what we just saw in the Battle for Mewni. Toffee, after getting into the wand and into the universe’s supply of magic, corrupted the entire thing without losing his own consciousness. That is a big deal, even more so when we see that his body is basically just a manifestation of the corrupted magic while Star still has her physical body in the space the magic is in. While it is possible that this was just a plot hole and done to make Toffee all the more threatening in those scenes (which worked extraordinarily well, mind you), a lot of fantasy and myths involving magic often mention how dangerous and corrupting on one’s body, soul, and mind it can be. And yet, here’s Toffee just swimming around and infecting the entire universe’s magic and making it unusable and not completely losing his mind. That is unbelievably impressive.
Plus, the idea of Toffee being Eclispa’s son could also explain some of his motivations. My best guess, Eclipsa probably had two children; a “human” (because let’s face it, you can’t really call the Butterfly family entirely human with that second form they have) daughter who successfully claimed the throne and continued the blood line, and Toffee who due to his monster lineage was most likely targeted to be killed as an abomination immediately after his mother’s defeat and was never going to claim any sort of power in Mewni. And got to witness firsthand the prejudice and hypocrisy against monsters by the humans. So it would make sense he would go rouge and kill one of Mewni’s queens. But it also explains the larger schemes he had in the show as well. He probably recognized the spell Moon used as one of his mother’s (maybe not right away), and once he realized where she had gotten it from and how it worked decided to use the situation to his advantage. Basically, he would have to die in order for his mother to be freed, but he was going to also paralyze the royal family and strip away their power as well. Hence the corruption and neutralization of the magic. Unfortunately, he only got half of what he wanted accomplished (or so it seems right now).
It also could play into making Eclipsa an even bigger threat. I’ve seen a few people saying how they hope Queen Eclipsa just ends up being that ‘weird grandmother’ character. And I think at first- under this line of thought- that’s how she starts out. Weird and maybe a little morbid at times but still nice enough and adores Star. But then she finds out what happened to Toffee and well… Hell is nothing compared to a grieving mother’s wrath.
But I’m probably just reading too much into things. It’s still a fun thought though, so I’m going to keep entertaining it for a while.
(P.S. Also, very minor circumstantial evidence, but did anyone notice that the candy Eclipsa was eating crunched? I can’t think of a type of chocolate bar that does that besides ones with rice crispies in them. And toffee bars. (Yeah, under this line of thought, I don’t think Toffee’s his real name. I think it was just a cute nick name his mother gave him and he started going by it full time after her defeat.))