Mohole

The “Mohole” is a hole located at the north pole of Moho. When the game first came out, it was caused by a terrain glitch, although anomalous forces around it would cause vehicles to accelerate toward it. Eventually, it was given its own dedicated biome and became a permanent part of the game.

Vallhenge

On Vall, there is a stone formation at that resembles Stonehenge.

Crashed UFOs

You can find a crashed UFO on the northern ice cap of Kerbin. There is also one on the Mun.

Toilet

If you destroy a level 3 Astronaut Complex, you’ll be able to see a toilet in the rubble.

Tut-Un Jeb-Ahn

There is a temple/pyramid located on Kerbin. If you crash into it, you will see that its name is Tut-Un Jeb-Ahn.

Nye Island

The “Nye Island” station might be a reference to Bill Nye.

Neil Armstrong Memorial

If you go to the Mun, you can find a memorial to astronaut Neil Armstrong, the first man to walk on the moon, who died in 2012.

Face on Mars

On Duna, there is a giant Kerbal face in the sand. This is most likely a reference to the “Face on Mars,” a hill on Mars that resembles a face in certain images.

Sagan Sea

The “Sagan Sea” biome on Laythe might be a reference to scientist and author Carl Sagan.

References on Parts

Numerous assembly parts include short references.

• The logo for the Z-100 and Z-400 Rechargable Battery say they are “Batt Man Batteries,” a reference to Batman.
• The Communotron 88-88 lists a hexadecimal number of 0x62656570, which can be converted to spell “beep,” and the serial number 04101957, which is a reference to the date October 4, 1957, the launch of the Sputnik satellite.
• Inside the SC-9001 Science Jr. bay, there is a biohazard sign and a warning of “Danger! Science Stuff!”
• The FL-T200 Fuel Tank has a failed re-entry drawn on it and crossed out.
• LY landing gear, which has “Lightyear” written on the tires, is a reference to Goodyear tires (and possibly also a reference to Buzz Lightyear from Toy Story).
• The Kerbodyne Launch escape system is designated A-004, which was the mission number of the final test of the launch escape system for the Apollo program.

Hitchhiker's Guide to the Galaxy references

The loading screen sometimes says “Answering Ultimate Question,” a reference to The Hitchhiker’s Guide to the Galaxy. The price of the EAS-4 Strut Connector, 42, might also be another reference.

Toy Story reference

The loading screen sometimes says “Falling With Style,” a reference to Toy Story, where Woody says Buzz is only “falling with style” instead of flying.