From the Super Mario Wiki
Butterflies are flying insects found in the Real World that appear in many games in Mario series and usually do so in groups. There are also many creatures that have a similar appearance to a butterfly.
Super Mario series
Super Mario 64
In Super Mario 64, there are a few stages (as well as outside Princess Peach's Castle) where there are Butterflies flying around. When Mario punches or goes near one, one of two things will happen: the Butterfly will either turn into a 1-Up Mushroom or become a black sphere and chase Mario until it hits him or hits something in its way; in either situation, it explodes. In this game, Butterflies are violet with white spots on their wings.
Super Mario Sunshine
In Super Mario Sunshine, Yoshi could eat certain types of butterflies to get different items. Yellow Butterflies yield regular coins, blue Butterflies yield Blue Coins, and green Butterflies yield 1-Up Mushrooms. In this game, butterflies are usually found fluttering around in groups, and are rarely by themselves like in Super Mario 64.
Super Mario Galaxy
In this game, butterflies are seen throughout various Galaxies. Even though they are used mainly for decoration, the player can collect a single Star Bit per butterfly by pointing the Star Cursor at the butterfly and moving the cursor around while still touching it, although this does not work while Mario or Luigi are on the Comet Observatory.
Super Mario Galaxy 2
In this game, a number of shimmering golden Butterflies appear on the Starting Planet in the Sky Station Galaxy (three also appear on the Peewee Geo Planet later in the galaxy), but only while Co-Star Mode is active. The player can use the Co-Star Luma to spin the butterflies in the same way as they would any other object. When spun, each butterfly releases three Star Bits each, after which they disappear. They also disappear the second that Co-Star mode is deactivated, though when it is used again, they return. If spun by the Co-Star Luma, they are gone for good. These golden Butterflies also appear on the Earth Planet, the Yoshi Tower Planet, the Fossil Planet, the Solar System Planet, and the Cone Planet in the Yoshi Star Galaxy.
Super Mario 3D Land
Butterflies also appear in some levels of Super Mario 3D Land. These particular butterflies have different colors, and cannot be affected by the player.
Super Mario World 2: Yoshi's Island / Yoshi's Island: Super Mario Advance 3
Butterflies made their first appearance in Super Mario World 2: Yoshi's Island, where they appear only as part of the scenery.
In Yoshi's Story, butterflies reappear as part of the scenery, however numerous butterfly sub-species such as the Teehee Butterfly and the Power Bee (known as Happiness Butterfly in Japan) appear as edible health restoring creatures.
Super Mario RPG: Legend of the Seven Stars
In Super Mario RPG: Legend of the Seven Stars, butterflies first appear in the opening with Princess Peach right before she is kidnapped. They later appear as part of the scenery in some areas of the game.
Paper Mario series
Paper Mario: The Thousand-Year Door
Mario Party series
Mario Party 4
They later appear in Mario Party 4 in the mini-game Butterfly Blitz. They have a small but major role; they are worth points when characters catch them. There are three kinds of butterflies that give players points to win; yellow butterflies are worth one point, red butterflies are worth two points, and blue butterflies are worth three points.
Mario Party 8
A Butterfly also made a very brief appearance in the Mario Party 8 mini-game "At the Chomp Wash". When a Chain Chomp sees it, the Chain Chomp attempts to chase it, which in turn knocks over several buckets of paint.
Names in Other Languages