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Vitality is a fun-looking romhack. For many, many rooms in the hack, the difference between what the two layers look like in the editor versus what they look like after being color-blended in-game is astounding. (Every Metroid hacker is openly jealous of how this looks.)
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Metroid 2 has some unused sprites that I still need to add to its TCRF article. There are 18 unreferenced enemy spritemaps that do not correlate with any extant enemy graphics page. Once I decide how best to represent them (or rather: when the motivation strikes again), I'll add them to the page.
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The earliest recorded Super Metroid speedruns were done in ZSNES. Given the atrocious stability of ZSNES, I recall (this was like 20 years ago) one of the runs desyncing during the final escape, meaning that we had to complete the run manually to see the final time.
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The series is named after American author F. Scott Fitzgerald's firstborn child, Seamus Metroid Fitzgerald.
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The eye doors in Super Metroid are technically not enemies, but rather tilemap-based actors ("PLMs" as the community calls them), meaning they belong to the same class as items, missile doors, scroll triggers, save stations, and mid-animation breakable blocks.
(one of these things is a lie)
thank you for the ask 
also who told you metroid was fun???