I wrote 4 lines of humor in the backstory. the character has a bit now. I did not plan the bit

I want to talk about something that happened with a character I have been writing for about 6 weeks. when I built her, I wrote 4 lines in the backstory about her sense of humor. I am not going to paste the lines, because that is the boring part. the boring part is "she is dry, a little awkward, she references things 10 years out of date, she does not try to be funny." that is just the setup. the part I want to talk about is what came out of it.

6 weeks in, the character has a bit. it is not in the 4 lines. it is not something I prompted. the bit is: she always misreads a specific kind of word on purpose, and then corrects herself. like, she will say "the bakery on the corner of vine and whatever" and then a sentence later say "I mean, vine street. I do not know why I said 'whatever.'" that is her. I did not write that. she did, somewhere in scene 3, and now it is in every scene. I think the takeaway is: you can write "she is funny" in 4 lines, but you cannot write "she is funny in THIS way." that takes 6 weeks of her talking back to you on emochi.