The Flipper featured in Super Smash Flash works exactly the same as it does in Super Smash Bros. Melee. Players can pick it up and throw it, when thrown, it will hover in the air and begin to spin. Any player who comes in contact with it receives damage. The Flipper continues spinning, while hurting other characters, and after some amount of time, it disappears. The Flipper works exactly the same in the reboot Super Smash Flash 2, being planted on ground and spinning only if players attack it or come in contact with it. It is worth noting that the Flipper appears alongside the Bumper, the item it replaced in Melee and conversely got replaced back by it in Super Smash Bros. Brawl.
Flipper is an obstacle from the game Balloon Fight, first appearing on Phase-07. A Flipper will remain motionless until a Balloon Fighter player or the Balloon Fighter enemies bump into it, making it spin uncontrollably. Coming in contact with a spinning Flipper will send any character flying away uncontrollably, putting them at risk of getting their balloons popped or, in the case of the player, get hit by a lightning bolt. After a while, the Flipper will stop spinning. Flippers in Balloon Fight are harmless, though they pose more of a nuisance; this is something that was changed on its conversion in Melee and SSF2 as an item where the Flipper is capable of dealing damage as it is spinning.
By mere coincidence, "Flipper" is also the name paddles in pinball machines (whom the Bumper originates) receive, but otherwise do not look the same or even have the same function.
A missing detail of the Flipper from Melee left out in SSF, got added back in SSF2: depending on which side the Flipper is viewed, one can see it has a red bolt on one side and a blue bolt on the other.