Kerbal

Kerbals are a species of short, green-skinned aliens from the planet Kerbin, the third planet from its sun, Kerbol. They stand at around 2 foot 4 inches, and have an enormously tall head, taking up an estimated 1/3 of their total body mass. Kerbals, as their culture suggests, are obsessed with space, rockets, and traveling into the unknown. They will often partake in long, arduous space travels to other planets in the Kerbol System

History
Similar to the human's BCE and CE dating system, the Kerbals use BEA and AEA, which stands for before exiting atmosphere and after exiting atmosphere, respectively

The Kerbal species developed in around 50,000 years, and their culture in only around 5000, this is an incredibly short amount of time for a race to evolve. their awkward walking style is attributed to their short legs and recent bipedal status, as it's suspected they only became a bipedal species in the last 100,000 years. In the year 627 BEA, a famous Kerbal astronomer, Kerbileio Kerman, discovered and named the 6 other planets in the local solar system and their moons. This is commonly agreed to be the start of Kerablkinds obsessive space-culture.

They got on Mun, the biggest moon of kerbin, just in 1 AEA. This is considered to be the most exciting part of Kerbal history: Jebediah Kerman, also known as The Great Kerbal, stayed an entire day alone in a little capsule while travelling to the Mun. His ship exploded on landing. Only the command pod survived, and he waited for the rescue mission, which exploded on landing on the other side of Mun, and Bill kerman also got stuck there. The last, and succesful, rescue mission was sent 2 days later. The ship succesfully landed on Mun, picked up Jeb and returned to Kerbin, while another rescue mission was picking up Bill.

Jeb has been also the first kerbal in space, the first kerbal on Minmus, the first kerbal on Duna and the first kerbal on Laythe, before dying in a test mission.

Biology
Kerbals have a skin color of any shade of green. They also appear to have hair growth explicitly on the head. Because of their short legs, they are slow walkers and runners.

Kerbals seem to be able to survive enormous amounts of time on very little food or water. They can also go for years living in confined spaces, which is very beneficial to their exploration of space.

Kerbals are very resilient in nature, capable of surviving and walking away from impacts that would kill many other species. They also have an inherent 'bounciness' as they tend to go limp and bounce off the ground when falling from a height before going on their way. They do not seem to be affected by radiation either, sometimes standing unshielded next to nuclear exhaust and showing no adverse effects.