The quirks. Not all of them are implemented, not all of them have that much of an impact on the game (at least for the time being most of them don't do much) so they're pretty much just a milestone of some sorts.
As for the blue potion. I even forgot it existed, had to check the code.
It's the potion that Lyx gave you for Pixie's storyline.
I wonder why it wasn't removed from the inventory after it was used...
Not like it does anything, aside from sitting in your bag being useless...