The Lion King

Cheat mode:
Press Right, A(2), B, Start at the options screen. Options for level select and invincibility will be displayed.

Unlimited roars:
Press Right, A, B, C, Start at the options screen. The sound of Simba as an adult roaring will confirm correct code entry.

Random start:
Hold Start on controller two and turn on the Genesis to start at a random level.

Hint: Pass through blocked locations:
In the first level where you become an adult (Simba's Destiny), there are three non-passable places that remain that way until you have defeated all of the Jaguars. To get past these without having to defeat all of the Jaguars, simply flip them with the flip move (X, Y, Z). Do this three to four times to get past without defeating all of the Jaguars.
Information in this section was contributed by David Forke.

Hint: Defeating Scar:
Get close to Scar then jump on him. As soon as you land use the slash attack repeatedly. Keep doing this until he moves on. On the last time you fight, keep on doing this trick until his face appears different. When this happens, lead him to the left and throw him over yourself by pressing Right + X, Y, or Z.
Information in this section was contributed by jam.