More Money : if you start a 2-player game at the same time, each one will be credited 3000 dollars. On the other hand, if the second player arrives afterwards, he will have 12000 dollars (you have just gained 9000 dollars).
Hidden Mission : there are several methods to play this mission, here is one : Beat the Mission 3 (The Forest Fortress) by destroying the heart of the fortress on the first blow (1st passage).
Various Little Ending Animations : at the ending screen (presented by Capcom), various little animations are shown dependent on how much Mechs were recovered, or if the Unicorn was recovered...
Mission 3, Forest Fortress :
Unicorn (+ a shield) - Destroy all trees without forgetting from the very start of the level to destroy the 1st tree on the left. The unicorn will appear spontaneously in front of the fortress.
Yashichi - Destroy the latest turret of the fortress, Yashichi is just on the right in bottom of the fire turret.
Mission 4, The Carrier :
Mech (1000 pts) - Just behind the 5th rock, on the ground level, a Mech which agitates a flag will appear.
Mission 5, Bomber called Bayson :
Mech (+ a T.Laser) - You must destroy the 39 rocks to see a Mech appear with a knife.
Mission 6, Missile Launcher :
Mech (10000 pts) - When the way separates in 2 ways, take the top while shooting at the base from the 1st pillar made of rock, a Mech will appear.
Mission 8, Battleship called Minks :
Mech (1000 pts) - After the 2 boats come from the left, place yourself at the top of the screen and shoot until a Mech with a rifle falls into water.
Yashichi - At the middle of the Battleship, we have a red turret, destroy it to release Yashichi.
Mission 9, The Arsenal :
Mech (1000 pts) - Behind the second building, a Mech with an umbrella hides.
Special Mission :
Mech (10000 pts) - An airliner will go down in the middle from the screen, then go up. Go to the left of the screen. When the plane starts to go down again, shoot until you see appearing the Mech overlapping a rocket at the bottom right of the screen.