User blog comment:PercyJacksonfan12/The bane of Zeus/@comment-4703034-20111224055641

Metis never got pregnant with the son. Zeus heard the prophecy of his and Metis' son overthrowing him but the son would be born after a daughter. He decided to get together with Metis anyway for one night and immediately regretted it. Metis had become pregnant with Athena from that one night. When Zeus swallowed Metis, Athena was born from his head sometime later and Metis remained in Zeus. As for Pan, i think that referred to that whole Luke/Knife thing.