The Doctor Vs. The Cyber King - The Next Doctor - Doctor Who - BBC
The Tenth Doctor defeats the Cyber-King from a hot air balloon. (TV: The Next Doctor)
A balloon was an inflatable bag filled with gas. It had a wide variety of purposes.
Transportation
In the 17th century, the Eleventh Doctor escaped from the Tower of London in a hot-air balloon, which witnesses called a "magical sphere". (TV: The Impossible Astronaut)
In 1851, Jackson Lake used a hot-air balloon called a TARDIS. (TV: The Next Doctor)
In 1863, the Third Doctor and Charlie Fisher used a hot-air balloon to help sketch a map of the Confederate lines. (COMIC: Backtime)
In India in 1926 the Fifth Doctor stole a hot air balloon in order to chase a steam train. (AUDIO: The Emerald Tiger)
In the 1940s, barrage balloons were used in the United Kingdom during World War II. (TV: The Empty Child)
In the 21st century, a picture of a hot-air balloon was on display in a space museum. (TV: The Seeds of Death)
On Spiridon, the Third Doctor improvised a hot-air balloon from plastic sheeting, enabling him and the Thals to escape the Daleks. This inspired him to take up hot-air ballooning as a hobby because he found it "most exhilarating." (TV: Planet of the Daleks)
When the Sixth Doctor took the TARDIS into Astrolabus' realm, it passed by a hot-air balloon. (COMIC: Once Upon a Time Lord)
Science
In the 1970s, Dr. Tyler used balloons to carry devices which monitored cosmic rays. One of these accidentally picked up a gell guard. (TV: The Three Doctors)
While on Storm Mine 4, Chub carried out experiments with weather balloons. (TV: The Robots of Death)
The Eleventh Doctor used two toy balloons to illustrate the difference between the main universe and the pocket universe in which Hila Tacorien was trapped. (TV: Hide)
Toys
In 1913, Daughter of Mine carried Lucy Cartwright's red balloon with her after taking over her body. (TV: Human Nature)
In 1914, Aphasia carried a red balloon with her. (PROSE: Human Nature)
As a child, Alistair Gordon Lethbridge-Stewart lost a red balloon. The Eighth Doctor later changed time to a minor extent so that he caught the balloon and returned it. (PROSE: The Shadows of Avalon)
Balloons were often used by clowns, such as Odd Bob the Clown, (TV: The Day of the Clown) Clara the Clown, (TV: The Celestial Toymaker) and Chuckles and Boris. (TV: Robot Gladiators)
A young Mikhail lost his balloon. The Eighth Doctor found him a new one. (PROSE: Reversal of Fortune)