Samus was originally planned to have unique sprites and animations for whether she was facing left or right. These sprites are still stored within the game's ROM. This animation idea would eventually be seen in Super Metroid.

On the box, it claims that the game is a "two player alternating game." This is not true, as the first multiplayer game was Metroid Prime 2: Echoes.

Yoshio Sakamoto, co-creator of the Metroid series, has stated that Metroid was influenced by the 1979 sci-fi movie "Alien". This is evident when considering the following:
• Both Metroid and Alien feature a female lead protagonist.
• The Nostromo's computer is referred to as "Mother" and the antagonist of Metroid is Mother Brain.
• The Xenomorph aliens and Metroids both have multiple stages of development, and the first stage of both species latch on to other creatures.
• The boss "Ridley" is likely named after Alien's director Ridley Scott.