1001 Video GamesThe NES version of Kid Icarus appears in the book 1001 Video Games You Must Play Before You Die by General Editor Tony Mott.
CameoPit appears as a playable character in the Wii game Super Smash Bros.: Brawl.
Famicom Disk System versionIn Japan, the second Famicom controller had a built-in microphone. It wasn't used in many games, but in the Japanese Kid Icarus version, shopkeepers sometimes gave players discount when they talked into it.
ManualOn page 38 of the U.S. Kid Icarus instruction manual (page 45 of the Japanese manual), the Syren enemy has bare breasts. It is perhaps the first (and only) female Nintendo character to sport breasts with nipples.
MusicThe Nintendo DS game Electroplankton includes sound effects and the dungeon theme music from Kid Icarus.
MythologyThe name "Icarus" comes from the myth about a boy who made wings out of feathers and wax and flew too close to the sun. "Medusa" was one of the three gorgon sisters whose looks could turn a man to stone. The boss "Pandora" is named after the woman in "Pandora's Box", who opened the box and unleashed all the evils upon mankind. The first boss is a two-headed dog that guards the Underworld Fortress, sort of like the Cerberus that guarded the entrance to Hades. The Syren is named after the sirens that would sing and lure sailors to their doom. The Uranos and Pluton enemies are named after Roman gods, Uranus and Pluto. Finally, Zeus is the main "god" of Greek myth.
Whoever translated the Japanese game and manual into English obviously didn't know anything about Greek mythology --- "Parthena" (Greek "Virgin") is written as "Palutena" (page 42), and the serpent "Hydra" is written as "Hewdraw" (page 35). We can be glad they didn't write "Medusa" as "Mehdewsah".