In my AUs where Tuba finds Grace first, then Simon, I like to imagine he does the thing where you accidentally call your teacher mom but with Tuba and Grave NEVER lets him live it down. Tuba is just happy they see her as a mother figure instead of just a denizen.
*Simon and Grace starting to argue in front of the Apex*
Simon: Let's do this in private. I don't want to be those people who argue publicly in the Train.
Random Apex Kid, interrupting: No. Don't do that, don't gaslight her. You started this!