Unlimited Heart trick:
     If  you leave and re-enter an area (go through a portal then back
into  the  stage  you  just left) all extra life hearts respawn on the
level.  If  you  go to say the mansion level you can get 2 extra lives
per  trip there (on second and third floor of the mansion). You can do
this unlimited times (or until you get tired of doing it at least).