Level select:
Press Right, Left, Right, Left, A, B, A, B at the title screen, after Higgins gets hit by the coconut,

Continue:
Enter the left cave in the first stage of the third level of Fern Isle. Continue game play until reaching the fourth skull. Jump up and down to find a bonus room and collect the "Hudson Bee". When game play ends, hold Left and press Start to continue from the last stage with all items.

Extra items:
Enter 0894 as a password for 99 of each item.