How did Athena get into Zeus' forehead?

The daughter of ZEUS and METIS, she almost didn't get born at all after GAIA predicted that doom, woe and Olympian take-over bids would be the result. ZEUS, remembering how he'd overthrown his own father, grew nervous at the thought of having a daughter with attitude.

With the birth rapidly approaching, he finally hit upon a plan and swallowed METIS just before the crucial moment. But it wasn't long before strange tapping and banging noises began to emanate from inside him. What on earth was she doing in there? He was getting a headache.

A little while of this and the pain began unbearable. HEPHAESTUS, hearing the cries of agony, came running in and bashed his dad over the head with an Olympic wrench.

And from the split in ZEUS's skull sprang forth his daughter ATHENA. She was fully grown, fully dressed and fully armed with newly forged weapons and helmet. That's what all the noise was about.