From the *starting position of a chessboard, you need to move the pieces to end up with 18 Queens following the chess rules at all times (this includes white moves first). The solution is the series of moves (not the final position, as there are plenty).
Having other remaining pieces is possible and allowed (e.g. a remaining bishop + the 18 queens and 2 kings).
* starting position FEN:
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
see also the orignial question on chess stackexchange