Throughout each playthrough of Camp W, you will unlock various "Memories." These are unique pieces of art associated with choices that you make. Your Memories are stored in your Grimoire, either sketched, painted, or taped onto the page next to the character they remind you of.
Above, you can see some of Wilfred's Memories.
Each playthrough will allow you to unlock 12 different Memories, from a selection of over 60. You'll have to go through the full game more than a couple times to see them all!