Captain Falcon has minor gameplay changes based on which alternate skin is being used. Presumably a programming oversight, the character's Environmental Collision Box (ECB), a small diamond that prevents the character from falling through stage environments and walking through walls, differs slightly between skins, meaning they have very slightly different widths for dealing with stage collisions/interaction (although hurtboxes remain the same on all skins). Ranked from thinnest to widest, Captain Falcon's default skin has the thinnest ECB, while the Pink, Blue, Red, and Black skins have wider ECBs, with the Green skin coming out on top with the widest.

If you turn off the music and select Captain Falcon on the character select screen, an extremely faint grunt obscured by the Announcer saying Captain Falcon's name can be heard. In the game's sound test, audio files can be found with "DEMO" attached at the end of them showing that every character in the game had similar planned sound effects on the character select screen, but only Captain Falcon's sound remains audible. Additionally, in the game's files, animations labeled "Select" and "SelectWait" can be found for every character in the game, many of which were either ripped directly from Super Smash Bros., are unfinished, or were repurposed in the final game. These are all presumably remnants of an earlier version of the character select screen that more closely resembled Super Smash Bros., where the character's in-game models were visible and used special animations and sound effects when selected.

There is an unused sound of the Boo's laugh from Super Mario 64 with the file name ST_GREATBAY_TKLE_LAUGH which would've likely been used for Tingle at the Great Bay stage.

In the game's files is an unused sound for when you get a Rare Trophy. This sound would later be used in Brawl, and as part of the character unlock screen in the subsequent three installments following said game.

When the game was rereleased under the "Player's Choice" banner in the US, the color of the game's title on the spine was inverted.

While almost every character requires eight frames after grabbing onto a ledge before they can do anything, Link is the only character that requires four frames before performing another action.

In an animated trailer for Boktai: The Sun Is In Your Hands!, a boy can be heard playing Super Smash Bros. Melee on a Nintendo Gamecube.

There are nine unused event match character tags stored in the game's files. The unused character tags are for Peach, Roy, Pikachu, Pichu, Ice Climbers, Zelda/Sheik, Mewtwo, Ganondorf, and Dr. Mario. They are never seen in game because none of the event matches force you to specifically play those characters.

Event 44: Mewtwo Strikes! is a reference to the first Pokémon movie, the main feature of which was titled "Mewtwo Strikes Back."

In the event the main objective is to K.O. Mewtwo without K.O.'ing Zelda, Mewtwo only appears 15 seconds into the battle.
Zelda also has a darker appearance in the event, which references how Nurse Joy, still under control by Mewtwo, disguises herself as the mystery woman in the movie.

There's an unused audio clip of Mario saying "Let's-a-go", possibly to have been used for a Final Smash back when they were considered for the game.

When receiving a Screen KO in Flat Zone, the characters will hit the screen in their standard tumbling animation as opposed to their animations used in the other stages.

The final roster was originally going to have a total of 20 characters (not counting Shiek). However, at some point during development, the developers felt the roster wasn't large enough, so several model-swap characters were added. These include Dr. Mario, Young Link, Falco, Ganondorf, Pichu and Roy.

During Pikachu's montage in the "Special Video" there is a part in mute city where there are two spinning platforms instead of just one like in the final version. Though it was changed in the final version, the two spinning platforms can still be seen on the Mute City trophy.

Mr. Game & Watch is the only character that cannot L-cancel all of his aerials, as the game reads Mr. Game & Watch's back-air, neutral air, and up-air as special moves. This was fixed in Brawl.

In Home-Run Contest, although the in-game counter stops at 9,999.9 ft, the signs in the stadium continue to count distance past 10,000 ft, although the stadium past 10,000 has no collision, and Sandbag falls through the world.

Wario was originally going to be a playable fighter in Melee but wasn't added due to time constraints. He even had one of the highest potentials of being in the game according to the Smash 2 polls. Sakurai even stated that he would've been included if he had time.

Ness is the only character who can't charge his down smash near a ledge, because his is the only one in the game that has a hitbox while it's charging.

Ayumi Tachibana, from the Detective Club series on the Famicom, was considered for the Super Smash Bros. Melee roster. She wasn't included because the character and the franchise she's in aren't well known outside of Japan.

Although the Dream Land stage looks perfectly normal, in Event 48: Pikachu and Pichu, the Dream Land stage is twice its normal size. It's unknown why, but some consider it to be because of the difficulty of the 3 -on-1 parameters of the event requiring a larger stage size.

According to early screenshots, the Yoshi's Island stage was originally going to have Jump Blocks.