THE TRUTH
Now THAT'S an interesting question. Let me see...
If i remember correctly, it all started in the Deltaverse server, an hispanic discord server i used to be in. The thing is, i don't remember what everyone else were talking about, all i remember is that all of a sudden i got pinged like 4 times in a single day on a single channel (literally never happens). So i went in to check what was happening, and it turns out for some reason someone decided to do the first mirrette x woostern ship art ever !!
here it is btw:
and... Yeah, people liked it, even Cebar and i thought it was a really cute pairing (after clarifying mirrette's age and making sure it was ok), so it's just been a thing ever since, i guess. Literally came out of nowhere and for no reason in particular, that i know of.
As for the in-universe explanation... I got nothing. Look, i know i've made some Mirrette x Woostern art myself, but truthfully, i'm not into uhhhh shipping culture, i just thought it was both funny and cute (and also i prefer trains).
So i think that's something someone else should answer for you. Cebar? Anyone else? No? idk
I guess you can come up with your own headcanon if you prefered.
Anyways, i hope that answered your question! Byee!