#(it's interesting when i occasionally get a question that comes prepacked with several assumptions—)

[ckret2]

What is the equivalent of the phrase "Oh my God" that Bill uses? Is he mentioning some god figure from his home dimension or is he using “Oh my me” or “Oh my Axolotl”?

He doesn't use anything.

Have you ever heard an atheist say "oh my big bang" instead of "oh my god"? In common usage, the word "god" in "oh my god" is merely part of a stock phrase and not a declaration of belief. In fact, changing "god" to another term would instantly make it more religious, since if you just say "oh my god" it's like "well maybe they believe in a god or maybe they're just using the phrase," but if you say "oh my [something else]" it's like "they DEFINITELY believe in [something else] so passionately that they changed the phrase just to emphasize how much they believe in it."

If Bill ever used the phrase, he would use it like a foreign word pronounced omaigohd that's just an exclamation that communicates a specific emotional meaning to English-speakers (anger, shock, excitement)—and he's not going to get all cutesy while speaking a foreign language to draw attention to something irrelevant. This exclamation isn't an avenue to announce his religious beliefs.

There ARE issues he feels passionately enough about that he'd break away from common English. Unless he's in "pretending to be human" mode, at any place where a human would naturally refer to themself as "a person," "a woman/man," "female/male," "she/he," Bill will refer to himself as "a shape," "a triangle," "triangular," "it," even in contexts where that sounds weird to the humans. His gender is triangle and that matters to him. Religion does not.

At any rate, there's no [something else] he could fill into the phrase. He knows for a fact that there are figures powerful enough to alter reality—he is one. He suspects on good evidence that there are even more powerful figures that can conjure an entire universe from nothing—he is not one. He considers "power" and "divinity" to be separate things, he doesn't think powerful figures are divine, and he doesn't think the divine is real. He thinks "god" is an artificial social label, like "king," that only exists when enough people concur that it's real and stops existing when enough people stop respecting it. He thinks "god" is what the weak call the powerful when they've been fooled into thinking the powerful deserve worship. He thinks he's one of the powerful that fools the weak. He doesn't think he's a god—except when he's lying to himself very well—but he loves how it feels when other people call him a god, so he encourages it. He doesn't consider anybody god, he doesn't obey or respect any authority, and generally the more powerful a being is, the more he dislikes them on principle. One trillion years ago, the beliefs he was raised with were the sort a white American boomer experiencing a religious crisis would insist are "spiritual but not religious." He briefly thought gods might be real in his youth, but never worshiped any.

But all that aside—his vocabulary simply doesn't include the phrase "oh my god." He doesn't want to imply he even might worship something—he's too proud and that pride is too fragile. If he has to make an exclamation, it'll be something entirely different—"Oh boy." "Oh, come on!" "You're kidding me." "Seriously?" "Whoa!" "Wow!" "No way," maybe hysterical laughter—whatever's fitting in a given situation. Several times in the fic I've had to go find a different phrase where if he was another character I could've just put "omigosh".