Teenage Mutant Ninja Turtles 3: The Manhattan Project

Additional continues:
In the Japanese version, press A, B, Right, Left, Right, Left, Down(2), Up(2), Start at the title screen. You can increase your continues after selecting a character.

Level select:
In the Japanese version, press Down(2), Up(2), Right, Left, Right, Left, A, B, Start at the title screen. The level selection screen will appear after selecting a character.

Cheat mode:
Press Up(2), Down(2), Left, Right, Left, Right, A, B, Start at the title screen before the demonstration starts. Note: For two player mode press Up(2), Down(2), Left, Right, Left, Right, A, B, Select, Start. Level select, extra lives, and sound test options will now be available.

Auto turtle selection:
Press Down(5) at the character selection screen, or Down(10) at the same screen for two player mode. After a turtle is defeated, the next turtle will automatically be selected randomly. Alternately, rapidly tap Left, Right repeatedly at the character selection screen.

Programmer message:
In the Japanese version, press Up(2), Down(2), Left, Right, Left, Right, A, B, Start at the title screen. A brief message in Japanese will appear.

Alternately, in the Japanese version, press Up(2), Down(2), Left, Right, Left, Right, B, A, Start at the title screen.

Save energy:
Repeatedly press A + B when low on energy to keep it from going down faster.

Hint: Defeating Bebop:
When he swings his mace at you, quickly jump kick over him and attack him back on.
Information in this section was contributed by Jason Hogan.

Hint: Defeating Groundchuck:
Contiguously attack him, but jump and do not waste time trying to attack him while he charges. When he uses a pipe on you, get close to him so that he cannot hurt you, but you can still hurt him. Be alert when he charges you again, and continue this cycle until he is defeated.
Information in this section was contributed by Jason Hogan.

Hint: Tubular Turbo Attack moves:
Perform the following moves by pressing A + B. Note: These moves will take a bit out of your enemies, but also do damage on yourself. They require one unit of energy per use. If you have one unit of energy remaining, you can still use the Tubular Turbo Attack move as long as desired, but watch out for enemies.
Information in this section was contributed by Jason Hogan.

Leonardo: Cyclone Sword Spin
Donatello: Knockout Roll
Michaelangelo: Kangaroo Kick
Raphael: Power Drill Attack

Hint: Overhead throw:
To throw any Foot-Clan over the Turtle's head, press Down + B. This is just as effective as the Turtles' special move and kills the robots with one shot, but takes no energy.
Information in this section was contributed by Cheezits007.

Hint: World Trade Center:
In the elevator level (after you defeat Shredder) you can see the World Trade Center in the background.
Information in this section was contributed by Jason Hogan.