Endings
Expert runners don't care, but here are the endings:
Animals
"The animals" are two non-hostile life forms: the Dachoras and Etecoons. They are not documented on this wiki because they cannot harm Samus. They demonstrate for the player shinesparks and wall jumping.
Samus can "Kill the Animals" or "Save the Animals" depending on her actions during the escape (e.g. Tourian Escape Room 1). It is much faster to kill the animals, so outside of special occasions like donation incentives during Games Done Quick, runners kill the animals.
Save the Animals
To save the animals, during Escape, make a detour from Parlor and Alcatraz to Bomb Torizo Room. Shoot out the right wall. An animation is shown of the animals leaving, but it's unknown by the creator of this page how the game tracks Save the Animals (see True Completion). There are StA runs that don't wait for the animation. https://www.shacknews.com/article/125534/what-is-super-metroids-save-or-kill-the-animals-incentive-sgdq-2021
A beginner should have plenty of time to save the animals if there's at least 1m30 remaining on the escape timer. An intermediate player should have plenty of time with at least 1m00. Vorpaledge saved the animals in about 20 seconds.
If the animals are saved, a small animation is shown during the ending while the planet explodes. A few pixels leave the planet heading directly to the right, signifying the animals escaped. (This is the canonical ending leading into Metroid Fusion.)
Note: You do not need to visit the animals before the escape sequence. You never need to visit their "home rooms" in Dachora Room and Etecoon Room, or otherwise see them.
Samus's Outfits: IGT
IGT aka "Clear Time" determines what Samus is wearing in this sequence.
Completion Percentage
Shown in game as "your rate for collecting items is". See Low%. This is the final screen in the game, and animates infinitely. By turning off the system / resetting the emulator here, the game will revert to the last time it was saved.
Links
https://www.reddit.com/r/Metroid/comments/qy5zz0/save_the_animals_running_gag_meaning/
