From the Super Mario Wiki
Banzai Bills (also known as Magnum Bills in Super Mario World TV series) are a larger variety of Bullet Bills that first appeared in Super Mario World. These huge bullets are often portrayed as predominantly black-colored and have shark smiles. They were the largest Bullet Bill sub-species, until King Bills were introduced in New Super Mario Bros. Wii.
 Super Mario series
 Super Mario World
In Super Mario World, Banzai Bills are fired from somewhere off-screen and travel slowly towards Mario. They can be defeated by jumping on top of them.
 New Super Mario Bros.
Banzai Bills reappear in New Super Mario Bros.. These Banzai Bills look like their Super Mario World counterparts, except that their coloring has a slight purple hue, and they have red shadows under their eyes to make them look more intimidating. In this game Banzai Bills are fired from huge Banzai Bill Blasters (unlike Super Mario World, where they are fired from an unknown source), and they only appear at the end of World 7-5 and 8-1 Additionally, these Banzai Bills travel very slowly, twirling in the air. Again, a simple jump is enough to defeat these massive enemies.
 Super Mario Galaxy
In Super Mario Galaxy, Banzai Bills once again only appear once, in the game's last level, Bowser's Galaxy Reactor. They do not home in on Mario's position like Bullet Bills, but they are still difficult to avoid because of their size. To avoid them, Mario has to wait until it passes by, or attempt to backflip over it. If a Banzai Bill touches Mario, he will be knocked down, which may possibly result in falling into the lava, and lose a wedge of health. They are indestructible in this game, as they cannot be jumped on, unlike in other games.
This is the first 3D Mario game to feature Banzai Bills.
 New Super Mario Bros. Wii
Banzai Bills appear again in New Super Mario Bros. Wii. They are mostly seen in World 7. In the World 7 Tower, they are used as obstacles, where Mario and co. must move up on a platform and Banzai Bills are shot at them. They can be jumped on to reach higher areas, therefore, still being just a bigger version of a Bullet Bill. However, just like most enlarged versions of enemies, an Ice Flower only freezes them for a quick moment, and then they will break out. This game introduces a sub-species of the Banzai Bill called the Missile Banzai Bill, as well as the even larger and indestructible King Bills.
 Super Mario Galaxy 2
They re-appear in Super Mario Galaxy 2, where they behave the same way they did in Super Mario Galaxy. Banzai Bills are first encountered in Sky Station Galaxy, and they later appear in Bowser Jr.'s Fearsome Fleet (during the fight with Megahammer), Fleet Glide Galaxy, and Bowser's Galaxy Generator. They can be defeated using a Rainbow Star or the Spin Drill, and award a large number of Star Bits. Notably, Banzai Bills are a lot more common in this game than in the predecessor. Like in Super Mario Galaxy, Banzai Bills cannot be defeated by jumping on them.
 Super Mario 3D Land
Banzai Bills appear in Super Mario 3D Land, they start appearing in World 8-5 and are more common in the special worlds. They move faster in the game and they don't spin around like the ones in Super Mario World. They can be defeated by jumping on them, touching them while in statue form, or using a Boomerang thrown by Boomerang Mario.
 New Super Mario Bros. 2
Banzai Bills appear in New Super Mario Bros. 2. Whenever Mario touches a Gold Ring, Banzai Bills turn gold. In this state, they leave a trail of two rows of coins behind them. They appear in World 5-5 and World 6-B. They also appear in the Coin Challenge Pack B and Platform Panic Pack DLC packs.
 New Super Mario Bros. U
Banzai Bills also appear in the Wii U title, New Super Mario Bros. U, where they make their only appearance in the level, Scaling the Mountainside. They operate in the same manner as in New Super Mario Bros. Wii.
 Super Mario World television series
A Banzai Bill makes a minor appearance in the Super Mario World cartoon episode "Mama Luigi"; however, they were renamed Magnum Bills, which is a possible combination of the names Bullet Bill and Magnum Killer, which is the Japanese name of Banzai Bills, for the show. In the episode, Mario, after narrowly dodging an attack by a Koopa Wizard, accidentally leaps into the path of a Magnum Bill. Luckily, Mario manages to avoid being hit by this Magnum Bill, which simply flies off into the distance.
 Super Smash Bros. Melee
Banzai Bills are a major threat in Super Smash Bros. Melee, where they appear in the Princess Peach's Castle stage, randomly entering the battle, colliding into the castle. Once burrowed into the wall, a Banzai Bill will detonate, causing massive damage to anyone caught in its explosion. The explosion will also press any buttons in range, activating platforms and ! Blocks. Also in Super Smash Bros. Melee, a Banzai Bill (as it looks like in Super Mario World) appears in the background of the Yoshi's Island stage (this applies to the returning stage in Super Smash Bros. Brawl).
 Mario Kart 7
Banzai Bills appear in the game Mario Kart 7. They appear in Airship Fortress, occasionally being shot out of the cannon alongside Bullet Bills; however, making contact with either of them simply knocks the player back.
 Super Princess Peach
Banzai Bills reappear in the game Super Princess Peach, where they act the same way they did in Super Mario World. This game also introduces a red, more dangerous variant of Banzai Bills known as Mad Banzai Bills.
 Mario Strikers Charged
Banzai Bills make a cameo in Mario Strikers Charged, in the Sand Tomb field. In this game, they only appear painted in one of the pillars in the background. Here, they are painted the same way they appear in Super Mario World.
 Mario and Luigi: Bowser's Inside Story
A Banzai Bill also appears in Mario & Luigi: Bowser's Inside Story. In Dimble Woods, Bowser saw Private Goomp, Corporal Paraplonk and Sergeant Guy carrying a Banzai Bill Blaster. They explain to Bowser that they are going to fire a Banzai Bill to Bowser's Castle, which was taken over by Fawful, as payback. The three, however, hadn't any Banzai Bills, so Bowser has to search one on his own. It seemed that a Wiggler on a farm had a Banzai Bill after Bowser pulled out his Giga-Carrot, which Bowser had to eat. He was originally going to use the carrot as a substitute for the Banzai Bill. After the carrot was eaten up, Bowser could choose to save or to get the Banzai Bill right now. If he asks for the Banzai Bill, the Wiggler gets mad because Bowser pulled out the carrot and ate it (which was quite ironic, since Bowser had to eat it for the Wiggler). After battle, Bowser finally got the Banzai Bill and gave it to Private Goomp, Corporal Paraplonk and Sergeant Guy. Then the Banzai Bill was shot to Bowser's taken-over Castle. However, Midbus and two other Goombas saw the Banzai Bill, and dodged it via flying.
 Mario & Sonic at the Olympic Winter Games
A Bullet Bill similar to the Banzai Bills appear in both versions of Mario & Sonic at the Olympic Winter Games, being called Big Bullet Bill. This gargantuan Bullet Bill captures the Snow Spirit, Icy in the DS version. The Big Bullet Bill is a rival of the fourth world and is faced in Blazing Bobsleigh (DS Version), Skeleton (Single Festival Wii Version), and Bobsleigh (Team Festival Wii Version). After being beat, the Big Bullet Bill will fly away, but not explode.
 Paper Mario: Sticker Star
Banzai Bill appears in the 3DS game Paper Mario: Sticker Star, in which Bowser Jr. fires one from his airship of Bowser Jr.'s Flotilla to prevent Mario and Kersti from reaching Bowser's Castle. Later in the level, Mario paperizes the Banzai Bill Blaster to shoot a Banzai Bill, making a huge hole in the flotilla.
 Trophy Information from Super Smash Bros. Melee
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