There are unlockable things in Super Smash Flash. There are below:
Clear Adventure on at least normal with Mario.
Clear Adventure on any difficulty with any character.
Complete 100-man melee with any character.
Clear 3-minute Melee.
Clear Adventure with the original 13 characters.
Clear Adventure with Sonic, Tails, and Knuckles
Clear Classic with Sonic on Very Hard Difficulty without getting Game Over. (Known glitch that you may be on any difficulty and it will still work)
Clear Adventure with Megaman on at least Normal Difficulty without getting a Game Over.
Clear Classic with Link on any difficulty.
Clear Adventure without losing any lives.
Clear Target Test with every character but him.
Clear Classic Mode with the original 13 characters.
Clear Adventure with Pikachu and Jigglypuff.
Clear Adventure with any character after having one hour of total play time.
Clear Adventure with Blade on at least Normal difficulty.
Unlock every character
Clear All-Star Mode with any character
All-Star is available after you have every character.
- The best way to unlock Final Destination and All-Star Mode is to unlock Mr. Game and Watch.