Congrats on all the followers! The aurors on a case find some eggs which they take back to MACUSA. They don't know what creature they could possibly belong to so they give them to Graves to keep until Newt can come and get them. He puts them in a little nest under his desk light to keep them warm. Only they hatch before Newt gets there and the ducklings imprint on Graves. So it become quite normal for Graves to march through MACUSA with an orderly line of ducklings waddling after him.