Background character

Background characters are, as the name implies, characters that appear in the background of some stages, they will appear in a stage that correspond to their home universe (i.e Shy Guys appear in Yoshi's Island). Note that background characters shouldn't be confused with stage hazards.

In Super Smash Bros.

Dream Land

• King Dedede appears floating in the background.

Saffron City

• Several flying and bird type Pokémon, including but not limited to, Pidgey, Fearow, and Butterfree fly across the skyline.

Yoshi's Island

• Shy Guys appears in the background.
• A Goonie, in it's Yoshi's Story design, occasionally flies in the background.

Congo Jungle

• Necky appears flying in the background.

In Super Smash Bros. Melee

Brinstar

• A Chozo statue on the main platform comes to life and briefly walks before settling down into its original position.

Brinstar Depths

• Kraid emerges from the lava and swipes at the stage, turning it clockwise or counter-clockwise.

Fourside

• A U.F.O which can be boarded hovers in close proximity to the Monotoli building.

Yoshi's Story

• Shy Guys fly over the stage, this time holding food.
• Pak E. Derm can be seen walking behind the scenery.

Jungle Japes

• Cranky Kong is seen walking back and forth in his cottage and rocking in his chair at various times.

Yoshi's Island

• A Lakitu and a Banzai Bill fly around in the background.

Mushroom Kingdom 2

• A Birdo moves in from either the left or right and shoots eggs into the battlefield and a Pidgit flies in on its magic carpet. Only the Birdo can be KO'ed.

Onett

• The meteor from the beginning of Earthbound can be seen pulsating at the top of the hill, while one of the car hazards is the Runaway 5 tour bus.

In Super Smash Bros. Brawl

New Pork City

• A statue of Pokey Minch from Earthbound appears in the right side of the stage.

Lylat Cruise

• Multiple ships appear battling in the background.

Smashville

• Villagers from Animal Crossing appear in the background.

Yoshi's Island

• For a third time, Shy Guys appear in the background.

Frigate Orpheon

• The Parasite Queen, Metroid Prime's first boss, appears in the background in Frigate Orpheon.

Pokémon Stadium 2

• Electivire, Drifloon, Hoppip, Skarmory, Cubone and Dugtrio all appear in the background of the various elemental transformations of the stage.

Green Hill Zone

• Tails, Knuckles, and Silver can be seen running up and down the loop-de-loop.