Sandbag

Sandbag (サンドバッグくん, Sandobaggu-kun) is an anthropomorphic bag character who was first introduced in Home-Run Contest in Super Smash Bros. Melee and has been a recurring element in the Super Smash Bros. series since then. Absent from the original Super Smash Flash, it makes an appearance in the reboot, Super Smash Flash 2, where, while filling similar roles, it makes its playable debut.

In Super Smash Flash 2
The Sandbag was first seen on McLeodGaming's Facebook cover photo. Sandbag was confirmed as a "joke" playable character as part of MG's 2016 April Fools' joke, and is a very unusual fighter that is not considered a main character from the main roster of the game; to this extent, it's the fact all its animations comprise of only three frames, it has ludicrously strong attacks, it cannot grab onto ledges, etc.

Prior its playable confirmation, the Sandbag was first seen in-game when online mode was implemented. Much like in Super Smash Bros. Brawl, the Sandbag is the practice opponent in the Waiting Room and players are given the option to practice combos or otherwise attack it while waiting for online matches to start. Unlike in the main Super Smash Bros. games, players can see the Sandbag's damage percent, grab it, Star KO and Screen KO it. The Sandbag also fills its traditional role in the Stadium game, Home-Run Contest, where players have to rack up its damage and launch it as far as possible using the Home-Run Bat or by other means. A new role the Sandbag fills is as the object of two Arena games, Sandbag Soccer and Sandbag Basketball. These modes put two teams on an enclosed stage field as they try to get the Sandbag into the opposing character's goal. As usual, the damage on the Sandbag will start to accumulate; this could mean the Sandbag can be launched at great speeds and that it could be hard to stop it once it is shot.

Trivia

 * Sandbag, Bandana Dee, Chibi-Robo, Mega Man, PAC-MAN and Bomberman are currently the only true "silent characters" in the game.