Fog machine

Fog machines (also referred to as Phantasmal Fog machines and simply machines) are devices created by Dr. Eggman used to spread the Phantasmal Fog at various sites around London in the Story Mode of the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The machines each produce a different color of fog, and can be shut down by destroying the dome on the top. The machines have a similar design to Dr. Eggman's other inventions, particularly Egg Pawns, with four fans on each of the legs to distribute the fog and a large glass dome on the top which produces it.

History
Dr. Eggman first mentions the machines in the episode The Night Before, where he asks Bowser to send some of his minions to guard the machines. A machine producing the blue fog at the Main Stadium appears in Foggy Foes, where it is being protected by Dry Bones and Dry Bowser. Mario and Luigi destroy this fog machine by each Ground Pounding on the dome, clearing up the fog an coming to the conclusion that Bowser's minions are responsible for it. After regaining her memory in The Mysterious Thief, Rouge leads Peach, Daisy, Amy, Blaze and the yellow, blue and purple Toads to another fog machine producing the pink fog in Hyde Park, which Blaze destroys. After Mario, Luigi and Toad arrive and ask her about Bowser's connection to the machine, Rouge remembers that it is the work of Dr. Eggman. King Boo and a Boo appear guarding a fog machine producing red fog in The Ghostly Tower, which Sonic destroys using a spin dash. Tails was initially disappointed by this as he wanted to see how the machine worked, though notes that the machine's destruction has caused the fog to disappear. After discovering the orange fog on Tower Bridge in The Blocked Bridge, Tails suggests that they try to find a fog machine in the area. After running into Jet in The Wind Master, Yoshi, Sonic, Tails, Shadow and Silver believe he may have caused the fog, though after finding out he has not, they ask him to help. Though he initially refuses, he agrees after Shadow defeats him, and then reveals that he has already found the machine. He tries to destroy the machine but fails, and Bowser Jr. appears to protect it. After Bowser Jr. is defeated in Enter Bowser?!, Shadow destroys the fog machine and Bowser Jr. accidentally reveals that it is Bowser and Dr. Eggman's work. Mario, Luigi, Toad, Sonic and Tails find Eggman Nega guarding the fog machine making purple fog at the British Museum in The Secret of the Fog, and though he initially promises to show them the location of the machine if they defeat him, he breaks his promise when he is defeated. The group track down the machine regardless and Mario and Sonic break it with another Ground Pound and Spin Dash. Wario finds a fog machine making yellow fog being protected by Dr. Eggman in Wario's Scheme, and after defeating Dr. Eggman tries to destroy it, though Dr. Eggman reveals that he had replaced the real machine with a 3D hologram. Wario and Waluigi track down Dr. Eggman and Metal Sonic in Stop Dr. Eggman!, and after defeating them in an Olympic Event and causing a diversion, Wario destroys the fog machine that they were protecting. Another fog machine producing green fog is found by Sonic in Corner the Koopa King!, where it is being protected by Bowser, though after he is defeated Vector keeps him away while Knuckles destroys the machine. Dr. Eggman acknowledges the destruction of the machines in Clear Skies Again, though replaces them using the full power of the fog amplifying system. Toad also mentions the lack of fog machines in A Rainbow In Fog.

A fog machine appears as the image on the Story Mode 2 badge.