I can see Jesus and his disciples sitting around one night and Jesus saying, "Hey, guys, a Pharisee, a Sadducee, and a Roman walk into the Tabernacle..."
And vesta, the best way to think of the Triune God is marginal at best.
Think of Him as water. It comes in 3 forms...solid, liquid, and gas. But it is still water. May call it other things, but when you come down to it, it's still water.
As for the Immaculate Conception, and how it happened, I can sum it up in two words.
God Spoke.