It's a mirror from page 62 ([link]) when Ms. P helps him learn how to use his illusion form, and it enables him to switch back to regular form after using illusion form.
Is it weird to admit that Jeff and ms. P look kinda cute together?...sorry if there's some huge age gap that I'm unaware of...just sayin what's on my mind. (P.S. congrats on your page 100 )