Sandbag

Sandbag is an anthropomorphic bag character who was first introduced in Super Smash Bros. Melee and has been a recurring element in the  series since then. Absent from the original Super Smash Flash, it makes an appearance in the reboot, Super Smash Flash 2, where it fills several roles, including its playable debut.

Character description
Sandbag is a white anthropomorphic bag with eyes whose sole role in the Super Smash Bros. series is to be attacked by other characters without fighting back. Its main appearance in the series is in the Home-Run Contest, a minigame where players are given 10 seconds to rack its damage up and hit it as far as possible using a Home-Run Bat. Sandbag has a visible damage percentage in this minigame, and it flies farther when hit at higher percentages, much like characters do. When hit off the starting platform, the camera follows Sandbag until it lands and stops moving, at which point Sandbag stands back up. According to its trophy descriptions in the series, Sandbag is not hurt by attacks, and it loves to see players wind up and let loose on it.

In Super Smash Bros. Melee, Sandbag is technically defined as a non-playable character, and therefore can be grabbed and thrown by players, and it is programmed not to move. From Super Smash Bros. Brawl onwards, however, Sandbag is defined as a "character item", and therefore it cannot be grabbed by regular or special grabs (except in Super Smash Bros. Ultimate). As well as its appearance in the Home-Run Contest, Sandbag may appear as an item during matches. It may release confetti and more items when characters hit it. In matches, Sandbag takes little horizontal knockback and cannot be KO'd by the upper blast line. Sandbag also appears in Brawl ' s Online Practice Stage, where players may practice by fighting it while waiting for online matches to start, as well as the various controls and customization test stages throughout the games used to test a player's controls, custom character, Mii Fighter, or Spirit Team.

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

As a non-playable character
Prior its playable confirmation, Sandbag was first seen in-game when online mode was implemented. Much like in the official Super Smash Bros. games, 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. Players can see Sandbag's damage percentage, grab it, and Star KO or Screen KO it like with any other character. 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 Sandbag fills is as the object of two Arena games, Sandbag Soccer and Sandbag Basketball, which put two teams on an enclosed stage field as they try to get Sandbag into the opposing team's goal. As usual, the damage on Sandbag will start to accumulate; this could mean Sandbag can be launched at great speeds and that it could be hard to stop it once it is hit.

Additionally, Sandbag serves as a background character in the aforementioned Sandbag Basketball, where multiple Sandbags appear on bleachers as an audience. It also appears as a background character on Waiting Room, which features one Sandbag standing on the left couch and another sleeping on the right couch. On the Waiting Room's Christmas theme, the Sandbag on the left couch wears a Santa hat and jumps happily, though the Sandbag on the right couch is absent.

Trivia

 * Sandbag and Pichu are currently the only characters in the  series to serve both a playable and non-playable role simultaneously.