There are three different endings for the game based upon completion time:
- Beat the game in over 10 hours to see Samus give you a thumbs up.
- Beat the game in under 10 hours to see Samus with her helmet off.
- Beat the game in under 3 hours to see Samus in her bathing suit.
The time isn't the only method to manipulate endings. After defeating Mother Brain, return to the place where you originally collected your bombs to meet some old friends. When you destroy the eastern wall, you give them the option to escape, and see them do so just before Zebes is destroyed.
The "Reset" Glitch
In old Tourian, go to the yellow door (the shortcut room) and go in. Do the VAR Beam glitch and shoot the DOOR FIRST and turn around and shoot again. The bar on top of the screen will be glitched. Now, enter the door. Old Tourian will be all misty from the beginning of the game. Turn the VAR Beam off and go save and turn off the game. Turn on the game and select the save file you saved on. Start and the intro should start. To confirm this, watch the first cutscene. Samus should do a Screw Attack and turn into her Gravity Suit. You'll see when the game starts, the Missiles are not there but the S. Missiles and other items should be there. Now you can play the game again and get more Missiles.
Face left and charge your normal beam. While charging, hit start to enter the weapon selection menu, and equip Charge/Ice/Wave/Spazer. Move to Hi-Jump Boots, and press left and A at the same time to equip the Plasma Beam; now you have all five beams equipped.
Press start to return the game, and still facing left, let go of the fire button. The murder beam will simply remain in the location from where it's fired, causing massive destructive power.
This will crash the game if you fire in any direction other than left. In addition, firing an uncharged beam or firing with a power bomb equipped will also cause a crash.
The most useful place to use this is on Mother Brain.