"Aw, it looks adorable on you !" is the sentence from you that is stuck in his mind. Earlier, you visited Purgatory Hall and you put a cat filter on Simeon and when you said he looked adorable, Simeon can’t seem to push that thought away. As Simeon couldn’t sleep, he walked in Solomon’s room and asked for him to do a potion. Solomon didn’t ask why and he did it anyways. He invited you over at Purgatory Hall, you accepted and once you got there, he opened the door having cat ears and a tail.