Background characters are cameo characters that appear in a stage that correspond to their home universe (e.g. King Dedede appears in the Super Smash Bros. stage Dream Land). Note that background characters should not be confused with stage hazards (though they sometimes play that role).
From Super Smash Bros.
Main article: Peach's Castle
Lakitu can sometimes be seen flying in the background.
Main article: Kongo Jungle (SSB)
Necky appears flying in the background.
Main article: Dream Land (SSB)
Main article: Mushroom Kingdom (SSB)
Main article: Planet Zebes
Main article: Saffron City
Main article: Super Happy Tree
From Super Smash Bros. Melee
Main article: Brinstar
A Chozo Statue on the main platform comes to life and briefly walks before settling down into its original position. It does not move in Super Smash Bros. for Nintendo 3DS. There is a large brain-like organism in the far background that shakes constantly, though it is not based upon any specific creature from the Metroid series.
Main article: Fourside
Porky Minch indirectly appears in his helicopter.
Main article: Great Bay
After three minutes have passed, the Four Giants appear on the hillside to push the falling Moon back into the sky (This is in reference to the fact that Link had three days to wake said giants and prevent the Moon from falling).
Main article: Jungle Japes
Cranky Kong is seen walking back and forth in his cottage, sometimes also rocking in his chair at some points. Flocks of Neckies can also seen in the far background.
Main article: Yoshi's Island (SSBM)
Main article: Yoshi's Story
Pak E. Derm can be seen walking behind the scenery.
From Super Smash Bros. Brawl
Regardless of stage and game mode, using Pokémon Trainer will have the Trainer himself stand on a platform in the background. As with the previous games, there are stage-specific background characters as well.
Main article: 75m
The original Donkey Kong appears on the top of the stage, as in the original game.
Main article: Distant Planet
A Red Bulborb occasionally appears, sleeping in the background. A Cloaking Burrow-nit can also be seen in Brawl, and four more can be seen with it in Ultimate.
Main article: Frigate Orpheon
Green Hill Zone
Main article: Green Hill Zone
Main article: Luigi's Mansion
Boos briefly appear from the rubble of the mansion when it collapses.
Pokémon Stadium 2
Main article: Pokémon Stadium 2
Shadow Moses Island
Main article: Shadow Moses Island
Main article: Smashville
Villagers from Animal Crossing appear in the background, depending on actual time of day and date, including K.K. Slider, Tom Nook, Blanca, Blathers, Booker, Brewster, (behind a counter, serving coffee) Celeste, Copper, Cornimer, Crazy Redd, Dr. Shrunk, Gracie (with her car), Gulliver (flying in his UFO), Harriet, Human boy (one of which bears a resemblance to Villager), Human girl Kapp'n (in the crowd and driving his taxi to the town hall) Kaitlin, Katie, Katrina, Lyle, K.K. Slider (on Saturdays at 8 PM, the same as Animal Crossing), Mabel, Pascal, Pete (flying in the background), Phyllis, Rover, Sable, Saharah, Joan, Timmy and Tommy, Tom Nook, Tortimer and Wendell.
Main article: Spear Pillar
Main article: WarioWare, Inc.
Jimmy T. and various Fronks appear in the background during several microgames.
Main article: Yoshi's Island (SSBB)
For a third time, Shy Guys appear in the background, with Support Ghosts, Chain Chomps and Goonies also occasionally appearing.
From Super Smash Bros. 4
Super Mario Maker
Main article: Super Mario Maker
Main article: Midgar
Umbra Clock Tower
Main article: Umbra Clock Tower
The angels Affinity and Inspired only appear and fly around in the background of Purgatorio, and occasionally the enormous Fortitudo comes close to the playing field and lets out a powerful roar, shaking the screen.
Super Smash Bros. for Nintendo 3DS exclusive
Main article: Spirit Train
Toon Link, in his Spirit Tracks incarnation, appears as a background character in the Spirit Train stage, where he drives the train. When playing the stage as Toon Link or Link, then Alfonzo will drive the train.
Main article: Find Mii
A Mii appears in the cage in the background, like the player's Mii in the original game Find Mii. In 3DS, this Mii is the Mii assigned to the player's console. In Ultimate, one of the Miis from the player's system is randomly selected instead.
Main article: Tomodachi Life
Miis appear in the background hanging out in the apartments.
Main article: Living Room
A few Nintendogs or a cat can appear as background characters in this stage.
Main article: Tortimer Island
Kapp'n appears ocasionally in his boat. Also, Leila, Leilani, or Tortimer can appear beside the shop depending on the variant.
Reset Bomb Forest
Main article: Reset Bomb Forest
Prior to the Reset Bomb's landfall, Viridi appears for a moment.
Main article: Prism Tower
Unova Pokémon League
Main article: Unova Pokémon League
Mute City (Ω form)
Main article: Mute City SNES
Captain Falcon can be seen riding the Blue Falcon in the background.
Super Smash Bros. for Wii U exclusive
Main article: Pilotwings
Miis appear on this stage, flying through the sky riding jetpacks. Unlike most Mii appearances, these Miis are pre-modeled and do not use the faces of Miis from the player's system.
Wii Fit Studio
Main article: Wii Fit Studio
Main article: Mario Galaxy
Mushroom Kingdom U
Main article: Mushroom Kingdom U
Town and City
Main article: Town and City
Gracie, Dr. Shrunk, Lloid, and Redd can be seen in the City variation, while Wendell, Pelly, and Sahara can be seen in the village variation.
Kalos Pokémon League
Main article: Kalos Pokémon League
-Alternatively, Rayquaza can appear, but as a stage hazard rather than a background character.
-Alternatively, Manaphy may appear instead.
- Alternatively, Ho-oh may appear instead.
Main article: Skyloft
Loftwings can be seen flying around.
Windy Hill Zone
Main article: Windy Hill Zone
Seven Animal friends (Flicky, Pecky, Picky, Pocky, Cucky, Ricky, and Rocky) from Sonic the Hedgehog can be seen in the background.
Main article: Pac-Land
Mother Fairy appears during the Fairy Land section, where she rewards the fighters with Flying Boots. When a round is completed, Ms. Pac-Man can be seen waving to the fighters as they return to Pac-Man's house.
New Donk City Hall
Main article: New Donk City Hall
The members of The Super Mario Players, including Pauline, appear on floating platforms, and on the ground in front of City Hall. Interacting with the band members causes them to begin performing "Jump Up, Super Star!". Captain Toad and the Odyssey can be seen in the background as well.
Great Plateau Tower
Main article: Great Plateau Tower
The Old Man from The Legend of Zelda: Breath of the Wild periodically floats onto the stage on his Paraglider.
Main article: Moray Towers
Main article: Dracula's Castle
Shadows of Dracula and Kid Dracula appear occasionally, illuminated by flashes of lightning. Other enemies make an appearance, each with an entrance based on how they appeared during their original boss battle in the Castlevania series: the Creature with Flea Man, Mummy, Medusa, Werewolf, Carmilla, and Death.
Main article: Mementos
Occasionally, Morgana, as the Morganamobile, will drive in the background of the stage, dropping off members of the Phantom Thieves of Hearts. These include Ryuji Sakamoto, Ann Takamaki, Yusuke Kitagawa, Makoto Niijima, and Haru Okumura. They'll react to the battle whenever a fighter is KOed. At times, a platform will lower down onto stage as well, which has a cracked screen on it. This screen has a chance of showing either Morgana running or Teddie, referencing the loading screens of Persona 5 and Persona 4 respectively.
Main article: Yggdrasil's Altar
The stage features many cameos from the Dragon Quest series, including Slimes, Tockles, Spirits of Lost Time, and Cetacea. Very rarely, a Liquid Metal Slime will appear in the background of the stage. Mimics can be disguised as chests on stage, attack players who try to open them.