The 2nd Doctor, the clown, the cosmic hobo, the original game changer. Upon deafeating the Cybermen in the Antarctic, the Doctor callapsed on the TARDIS floor. Just as Ben Jackson and Polly Wright were about to help him, an amazing event happened. Before their very eyes a mysyerious glow covered his body triggering a change in his physical appearance. Gone was the face of the old man they once knew, now before them, a face of an impish little man with a mop head of hair; resembling a Beatles haircut. The change left his companions baffled and shocked. There wouldn't be much time for explanation once the TARDIS landed on the planet Vulcan where much to the chargin of the little man and his friends, the Daleks were mapping their latest attempt in universal domination. The adventure alone proved to the young Seaman and his "Dutchess" that the Doctor is the same man they met sometime ago.
For sometime, the trio found themselves neck deep in Cat People, San Fransisco, Hollywood 1947, Pluto, the shark-like menace the Selachians and the Battle of Culloden. It was that particular adventure that see the TARDIS crew welcoming their new friend, the Highlander Jamie McCrimmon. Further travels the four friends had included Atlantis, the Cybermen's invasion of a moonbase, the Macra, the Roundheads, a rematch with Selachians (at a bank no less!), the Vist, and the Second World War. Things would come to a end for the four as their encounter with the Chameleons on Earth 1967 led to Ben and Polly remaining on their very timestream they left from long ago.
(Above; left to right: Ben, the Doctor, and Polly/ Below; the Doctor, Polly, Ben, & Jamie)
Upon the chase to retrieve the TARDIS, which was stolen from Gatwick Airport, the Doctor and Jamie would come across an even bigger mystery. The trail lead to a 1866 Victorian shop owned by one Edward Waterfield who along with his associate Theodore Maxible were experimenting in time travel with unlikely allies...the Daleks as, unknown to him held his only daughter Victoria captive.
(Left to right: Victoria Waterfield, the Doctor, & Jamie McCrimmon)
The Doctor defeated the Daleks, this time by manipulative means (this side of the Doctor wouldn't return until his 7th incarnation) leading to a brief strain on his and Jamie's friendship. With the Daleks and their Emperor destroyed and her father among the casualties, Victoria was left orphaned until the little man took her in. The trio had further adventures: the Cybermen expedition on their surrogate planet Telos, dealing with the Great Intelligence, The Great Space Elevator, the Ice Warriors, China's first Emperor, the Doctor's doppleganger of a dictator, and returning to a familar planet inhabited by the Menoptra and the Zarbi. These adventures a lot for Victoria to deal with which eventually led to her leaving the TARDIS to stay with her new family, the Harrises. For the Doctor, it was a small blow while it was a crushing type to Jamie; who was very fond of the young woman. Sometime later and a few short trips the Doctor and Jamie found themselves on board a wheel in space where it would be under seige by Cybermen. With the help of young astrophysicist Zoe Herriot, the Cybermen were defeated and Zoe became the latest member of the TARDIS crew. Around this time, the Doctor began using his sonic screwdriver; which would be the norm until his 5th incarnation.
(Left: the Doctor, Jamie, and Zoe; Right: Brigadier Lefhbridge-Stewart)
The Doctor's adventures went from the base under seige to the bizarre in a instant. Dealing with Dominators and their Quarks, a land of fiction (even Jamie gets his face altered for a brief time), and the Cybermen's latest scheme on Earth with the assistance of Tobias Vaughn. That adventure led to the Doctor reuniting with a soldier who'd since became his long time friend and ally: newly promoted Brigadier Alastair Gordon Lethbridge-Stewart. Following adventures included the Krotons, the deadly Mykloi, China 1800, reverse sexism on a planet ruled by women, additional confrontations with the Ice Warriors and Selechians, chaos on Rosemarinus, and being held captive by Space Pirates. The good times would come to a screeching hault in the form of their enounter with the War Lord and his War Chief (who was another member of the Doctor's people). The event lead to the Doctor contacting the Time Lords which led to his trial and the departure of Jamie and Zoe (leaving only their memories of their first encounter with him intact). Declared guilty, the Time Lords sentence the Doctor to exile (aside from doing a few things for their Celestial Intervention Agency) and forcing the little man to regenerate in the process; in a way the 2nd Doctor was executed.