Nine 1-Ups:
  Go directly to the Level 1 exit and fire at it five times. You'll warp to a
  secret section containing several flashing exits. Ignore the exits for the
  time being. Turn around and move down the hall, to the left, you'll find a
  floating ball in the alcove that contains nine extra lives. Take one of the
  exits to move on to Level 2 or, if you locate the right flashing exit, warp to
  Level 10.

Cheats von Martin Strohmeier - Martin.Strohmeier@t-online.de