I just discovered a bunch of secret dialog if you try to name yourself names that appear in game
Dont forget to start with a capital letters
a good example is simply "Timber"
There are many more and I love this attention to detail.
All the ones I have found with unique dialog ( many others just say "that name is taken") Timber, Senbei/Osmanthus, Time/Space/Nil, Syrup/Gumdrop, Pastille, Treat, Mochi, Moxie, and Trick. Most other characters with confirmed names in game just say "that name is taken"