Forbidden Islands:
Select the normal game option. Move Skweek or Skruch over the "O" in
the word "Gargouil Land" at the map screen. Scale the screen until
your character can not fly lower. A snorkeling furball will appear.
Carefully position your character over the furball and press Option 1.
The Forbidden Islands may now be accessed,

Extra lives:
Scale on the small island directly to the right of the "Welcome
Island" in the top right corner of the dark blue spot. Hover over the
Skweek next to a palm tree and press Option 1 for two extra lives.

Extra coins:
Scale over the large body of water in the "Pagalagos Island". Hover
over the Skweek and press Option 1 to collect 3000 extra coins.