How I can get the mega boobs and mega cock for my character?
I don't think megacock is a thing yet, but you can get megaboobs by progressing to the endgame. It requires completing almost everything in the game to unlock, so it's not really worth covering specific requirements unless you're already close and done almost everything. Just follow the fortune teller and logbook hints until you get there.
(If you're already done most things and just want to enable it, go to the UFO and talk to the alien again.)