Parents, what were the most unexpected costs in the first 5 years?

There are costs like formula, diapers, healthcare, toys, and miscellaneous (car seat, crib, diaper bag), etc.

Then there’s the hard hitting costs associated with daycare, which luckily we won’t have to deal with because my mother in law lives with us.

Aside from that, what’s the most unexpected costs in the first 5 years? I’m in medicine, so my income boost will be very significant in 5 years from now. Until then I’ll be on a resident salary (80-100K).