Fake Bowser

Fake Bowsers (or Bowser Imposters) are various standard enemies that were transformed by Bowser's black magic into duplicates of himself. They first appeared in Super Mario Bros.

Super Mario Bros. / Super Mario Bros.: The Lost Levels
Mario has to fight seven Fake Bowsers (one in each castle) before he can reach Bowser's Castle and fight the real one. Defeating a Fake Bowser with five fireballs reveals that they are really just common enemies disguised as Bowser. The enemies and their abilities are:


 * World 1: Goomba - fire
 * World 2: Green Koopa Troopa - fire
 * World 3: Buzzy Beetle - fire
 * World 4: Spiny - fire
 * World 5: Lakitu - fire
 * World 6: Blooper - fire and hammer (NES) / hammer (SNES)
 * World 7: Hammer Bro - fire and hammer (NES) / hammer (SNES)

Super Mario Bros.: The Lost Levels additional worlds:
 * World 9: Bowser - fire and hammer (FCD) / Bowser - hammer (SNES)
 * World A: Goomba - fire (FCD) / Red Koopa Troopa - hammer (SNES)
 * World B: Green Koopa Troopa - fire (FCD) / Green Cheep Cheep - hammer (SNES)
 * World C: Buzzy Beetle - fire (FCD) / Bullet Bill - hammer (SNES)
 * World D: Spiny - fire (FCD) / Bowser - hammer (SNES)

The "You VS. Boo" challenge of Super Mario Bros. Deluxe:
 * 1-4: Green Cheep Cheep
 * 2-4: Bullet Bill

In Super Mario Bros.: The Lost Levels, Worlds 8-4, 9-3, and D-4 feature a Bowser with a brown body and teal head and shell instead of the usual colors. This is due to the fact that it's the castle palette for green enemies including Bowser who are changed to their overworld palette at the end of the castle. Defeating the blue Bowser with fireballs doesn't turn it into an enemy, and Encyclopedia Super Mario Bros. states that its identity is unknown, making its status as a Fake Bowser ambiguous. This blue Bowser also breathes fire and throws hammers in all levels encountered except in World D-4, where it only breathes fire. In Super Mario All-Stars, their colors are changed to be the same as Bowser's, making it ambiguous whether it's the real Bowser or a fake.

Super Mario Advance 4: Super Mario Bros. 3
In Super Mario Advance 4: Super Mario Bros. 3, a Fake Bowser appears as a boss in the World-e level Classic World 1-4, where it plays a similar role to that played in Super Mario Bros., though it looks identical to the game's real Bowser. It is revealed that the Fake Bowser is a Goomba if it is defeated with fireballs.

Super Mario 3D Land
Fake Bowsers appear in the Nintendo 3DS game, Super Mario 3D Land. They have spiky raccoon tails, and they attack like they do in Super Mario Bros., breathing giant fireballs and jumping around the stage, though they do not throw hammers.

However, unlike in Super Mario Bros., only two Fake Bowsers appear: one in and the other in. They are also immune to projectiles. In order to defeat a Fake Bowser, Mario or Luigi has to press a switch at the end of bridge to make it collapse and send the Fake Bowser into the lava. After falling into the lava, Fake Bowsers bounce upwards and show their true forms (a Goomba in World 1, and a Magikoopa in World 5) with a Super Leaf beside them. The Prima guide refers to Fake Bowsers as Tail Bowsers.

Super Mario Run
In Super Mario Run, Fake Bowsers appear at the end of the Fortress levels in Worlds 1, 3 and 5. They are a Goomba, a green Koopa Troopa, and a Buzzy Beetle, respectively.

Mario & Luigi: Superstar Saga
A Fake Bowser makes a cameo appearance in Mario & Luigi: Superstar Saga. It is seen in a special area inside Bowser's Castle, which is a side-scrolling level imitating a Super Mario Bros. level, and appears at the end of that level. The Fake Bowser appears to be made of cardboard, and Mario must run underneath him and hit the axe to make him fall.

Mario & Luigi: Paper Jam
While a Fake Bowser never appears physically in Mario & Luigi: Paper Jam, one appears on a Battle Card, taking its design from Super Mario 3D Land.

Mario & Sonic at the Sochi 2014 Olympic Winter Games
A Fake Bowser appears as a boss in Mario & Sonic at the Sochi 2014 Olympic Winter Games, specifically in the Mario World version of Dream Figure Skating. The appearances of the stage and its boss are based off Super Mario 3D Land. He chases the team across a giant collapsing bridge, spitting fireballs at them. The team must hit four buttons at the same time to cause the Fake Bowser to fall into lava, where he turns into a Goomba and a Super Leaf.

Super Smash Bros. for Nintendo 3DS / Wii U
According to one of the tips in Super Smash Bros. for Wii U, Bowser's eighth alternate coloration in these games is based upon the Fake Bowser that appears in World 8-4 of Super Mario Bros.: The Lost Levels.

Trivia

 * The World 3 and World C (original) Fake Bowsers are the only Buzzy Beetles that can be defeated by fireballs, and the World C (All-Stars) and "You VS. Boo" 2-4 (Deluxe) ones are the only Bullet Bills that can be defeated by fireballs.