While not exactly a character, per se, I belive that Teletran One has been an integral part of the Transformers mythos from the very beginning, and deserves his own entry on this site.

Teletran One is the central computer of the Autobot spacecraft, the Ark. When the Ark was launched from Cybertron four million years ago, it was attacked by the Decepticon warship, the Nemesis, after traversing a meteor shower. Autobot commander Optimus Prime put the Ark on a suicide course, sending it crashing to the third planet of the Sol system - a world that would come to be known as Earth. The Transformers were all thrust into emergency stasis by the crash, and lay dormant, imbedded in a volcano. It was not until four million years later, in the Earth year 1984, that the volcano erupted, the explosive force jarring Teletran One into activity again. Teletran immediately sent out SkySpy probes, to ascertain the dominant lifeform on the planet - but its damaged sensors detected only machines, and so it set about rebuilding Autobots and Decepticons indescriminately, giving them the ability to alter their forms into those of Earthen machines. The first to be repaired was Skywarp, who then saw to it that the other Decepticons were rebuilt. When the Decepticons pulled out of the Ark, the Decepticon Air Commander, Starscream disobeyed orders, and fired on the Ark. The shockwave from his blast knocked Optimus Prime into the repair beam from Teletran One, and he was reactivated.

After initial confrontations with the Decepticons, the Autobots enlisted the aid of two humans - Spike and Sparkplug Witwicky. Spike, while writing in his journal outside of the Ark, found a small tape player lying on the mountainside - thought unbeknownst to him, it was actually the Decepticon Communications Officer, Soundwave. Spike brought Soundwave into the Ark, where he and his subordinate Ravage accessed Teletran One and stole information on Earth. After several more attacks, the Decepticons obtained enought energy to power their new space cruiser, but the Autobot Mirage was able to drive it beneath the sea.

Teletran One is a highly sophisticated machine, with numerous capabilities. Teletran is capable of diagnosing and repairing injuries to Transformers, as well as scanning and identifying them without fault. Teletran is linked to a ring of its personal SkySpy satellites which each have hi-tech scanning relays. It seems to be somehow linked to the Dinobots (Ref: "Heavy Metal War"). Teletran possesses a huge database of information on the history of Cybertron and the Transformers, and has very powerful radio broadcasting capabilities. Teletran is in control of all the major systems within the Ark.

Teletran One has been important to the Autobots ever since they crashed on Earth. Megatron once sent the Constructicons into the Ark to destroy Teletran One, so he could duel Optimus Prime and cheat without fear of being discovered. The Dinobots saw off the Constructicons, thankfully. Teletran constantly provided information for the Autobots on numerous occasions, for example, during the time of the fiasco with Cosmic Rust. Once, Teletran was short-circuited by an energy imp created by Megatron named Kremzeek, who jumped inside his circutis, and scrambled his databanks, causing Teletran to broadcast a scrambled message out to the world that Martians were going to invade and steal Earth's ammonia!

Teletran One served the Autobots needs well, and probably had a hand in the design of the majestic Autobot City, towards the end of the 20th Century. Regrettably, in 2006, while repairs continued on Autobot City, which was damaged in a Decepticon strike in 2005, the Decepticon city of Trypticon utterly destroyed the Ark, and Teletran One with it.