It took a couple nights my first playthrough. My second he showed up the very first time I did a long rest. Never used the tadpole.
It might be after you speak with Nettie? Or maybe after the first failed attempt at removing it in general.
I kind of like that he shows up early. He's the only signifier the player gets that the tadpole isn't about to transform you any second now and that you can relax and explore a bit.
