Marvel Comics continuity
Four million years ago, shortly after the crash of the Ark, the Ark's computer detected Shockwave landing on the planet in the Antarctic land-out-of-time. The Ark used the last of its capabilities to revive five warriors and rebuild them to transform into the Savage Land's dominant lifeform: dinosaurs.
The Ark's computer would later rebuild the Autobots and Decepticons in new Earth forms when Mount St. Hilary exploded in 1984 and awakened the ship.
The Transformers aboard the Ark were damaged and went into stasis lock after the Ark crashed into Mount St. Hilary. Four million years passed and then in 1984 volcanic activity stirred the half-buried Ark, awakening Teletraan I, the computer system aboard. Teletraan I sent out a Sky Spy satellite to reconnoiter this new world, and scanned examples of terrestrial machinery in order to repair the Transformers and reformat them into new alt modes. For some strange reason, the Autobot computer was unable to tell Autobots from Decepticons.
Dreamwave comics continuity
IDW comics continuity
Protoform Transformers are able to get new alternate modes by using the DNA scanned from the lifeforms of the nearby environment.
When scanning, the "scan beam" emitted from the DNA scanner can analyze the DNA data scanned from the lifeforms immediately. If the device scans a corpse or fossils, it is able to reconstruct the lifeform's appearance during its lifetime, such as the alternate modes of Megatron, Dinobot, Terrorsaur and Nightscream.
After retrieving the scanned DNA data, the data are sent to the C/R Chambers or C/R Tanks. The Protoform Transformers have to enter the C/R Chambers or C/R Tanks to get their new alternate modes.
There is also a DNA scanner mounted on each stasis pod, in order to get the DNA from the local lifeform of the planet where the stasis pod land on.
Some of the Protoform Transformers have DNA scanners inside their bodies, such as Nightscream.
- After falling into a hole, Nightscream became unconscious. During that time, the DNA scanner inside his body was activated and scanned the fossils of a native big bat on the planet Cybertron, making him gain a bat-alternate mode.
- According to Botanica, she scanned the DNA from the plant on the planet she landed on.
Beast Wars II
Robot in Disguise
The Transformers scan their modes too - animals as well as vehicles. However, an actual vehicle is not needed: a good enough representation of one will work just as well. Jolt and the rest of the Recon Mini-Con Team scanned their vehicle modes from Coby's motor magazine, and many Autobots are seen to scan holograms of vehicles projected by other Autobots. In fact, the scanning of holograms is used far more often than the scanning of an actual vehicle. However, the kibble of yet-unscanned vehicle modes is glaringly obvious, with every Transformer happening across vehicles or representations of vehicles that look exactly like the vehicle parts already on them. This is disguised in later episodes by obscuring the newly-arrived Transformer before the scan (such as the glow of the reformatting of the Cybertron Defense Team not dying down until they'd scanned new vehicles, or Crosswise not fully breaking free of the ice until after scanning a car.)
Transformers (2007 film)
When the Autobots first arrive on Earth, they can be seen blowing stuff up and scaring humans and having themselves mistaken for the tooth fairy. Then they take on their Earth forms. From Jazz's perspective, you can see him scanning the different parts. Their original Cybertronian forms change to accommodate the various parts and kibble that their Earth vehicle forms have. Other than that, it just appears as though they have to look at the vehicle to change into it. See also:Trans-scan
The process by which the main Autobots scan their Earth vehicle modes is nearly identical to the process seen in the Generation One series premiere: A small robot similar to the Sky Spy arises from the ship to scan vehicles with a yellow box effect. Here, it's called "Mode-scan." Within the ship, however, a small booth rises from the floor, with each Autobot entering to have the new forms applied to them. Decepticons are seen to scan vehicles themselves, without needing outside help. Their box effect, as with much about the Decepticons in this series, is purple. Exactly how and when the Cybertron Elite Guard scanned their Earth altmodes is unknown. This raises the question as to whether or not Autobots have the ability to mode-scan on their own: thus far, only Decepticons have demonstrated the ability, though it doesn't necessarily prove that the Autobots don't have it.
In a manner similar to the live-action movie, every Transformer's robot mode is altered to reflect the new vehicle mode, giving almost every character a Cybertronian form and an Earth form.
Revenge of the Fallen film
Transformers do not change their appearance after scanning a vehicle. The scan itself is emitted from the eyes and consists of a wide green triangle-shaped beam.