Canon Discontinuity: Super Smash Flash 2 is officially considered a reboot and not a sequel, as explained briefly here, thus pushing Super Smash Flash out of canon.

Collision Damage: The enemies in Adventure Mode, along with the Mario brothers, the Sonic characters, and Samus while they're jumping.

Combos: While normally impossible due to the primitive engine, some could be performed due to a bug with some characters, namely Mario, Zelda, and Captain Falcon.

Early-Installment Weirdness: The second game seems much like the official Smash games. The first, not so much.

Game-Breaking Bug: The famous "One-Hit KO" bug, which allows some attacks to kill instantly at just 50% while standing still. Unfortunately, though, Master Hand and Crazy Hand's attacks have this trait, too, which makes unlocking Inuyashanote Clear Adventure Mode without losing a single life nearly impossible without cheating.

Gender Flip: The announcer is female here, voiced by Kira Buckland.

Hitbox Dissonance: Samus' machine gun moves in the first game. The machine gun fire has a hitbox. Not Samus' gun, the actual machine gun's bullets have hitboxes. This can be seen in Adventure mode levels where if you use the machine gun specials at certain ranges, Samus will be the one to take damage and be knocked back. It's like something out of Daikatana.

Mercy Invincibility: While the Smash games weren't known for this, it becomes a point in the first Flash which also averts this in the worst possible way. Especially in Adventure Mode, where just brushing against an enemy in any level could result in your damage skyrocketing to maximum in a very short time. A normal enemy can do this.

Misbegotten Multiplayer Mode: You could battle it out with two players... but the camera always follows the first player, ignoring the second.

Multi-Slot Character: Much like Super Smash Bros. Melee, the first Super Smash Flash has two playable Links from Ocarina of Time; one being his adult form and his young form. Sonic is also playable in this game, alongside his Super Form as an unlockable separate fighter. Compared to normal Sonic, Super Sonic has higher jumps and damage output, but ironically has slower attacks and a larger hitbox.

Original Character: Blade the Hedgehog and Blue the Hedgehog, sword-wielding Sonic the Hedgehog fan characters someone made who ended up as characters in Super Smash Flash.

Before the roster was revised, Super Smash Flash 2 had those two return, and added Azrael and Spikeman.

Punched Across the Room: A Game-Breaking Bug allows this to happen with many normal attacks if one stands completely still as the opponent approaches.

Shockwave Stomp: Mr. Incredible's ground down attack.

Spotlight-Stealing Crossover: The official Super Smash Bros. is a crossover between various Nintendo franchises, yet the most repped franchise in the first Flash game was Sonic the Hedgehog, which got five characters (seven if Blade and Blue are counted).

Swap Fighter: Kirby became a Swap Fighter with Meta Knight due to technical limitations of the developer being unable to implement the copy ability.

Two Girls to a Team: More like "Two Girls to a Roster." Not counting Jigglypuff, who's gender is ambiguous, the only female characters are Zelda/Sheik and Samus Aran.