Who the hell does that!!!??
My neices' father showed up to her birth (lo, these 16 years ago) with his new - pregnant - girlfriend on his arm. I was not amused.
When my 3-year old niece developed seizures from a sinus infection he refused to get treated, I had to take him aside and let him know that the little girl was his insurance policy. The moment anything else like this incident happened, or she looked upon him as anything less than the ideal father, I promised him that I would disappear his ass right off the face of the universe.
Needless to say, he's been a lot more responsible a parent - at least in my presence - since then.