After Neil Armstrong's death, the developers of the game put a memorial to him on the Mun, at the latitude and longitude that Apollo 11 landed.
Just before version 0.21, Kurt J Mac embarked on a mission to bring all of his errant kerbonauts home alive. Across a three part episode, he pulled this off with style. Many people, moving from one version to the (save-incompatible) next would simply leave their Kerbals where they were and move on. Kurt took it to the next level when he successfully retrieved everyone from various edges of the Kerbin-sphere.
On the Day of the Dead, KSP posted a short video on their YouTube page. A Kerbal lovingly arranges candy skulls on an altar before being called away. The camera switches over to see that the altar is dedicated to three deceased Kerban astronauts, whose spirits leap from the photo and inhabit the candy skulls. They sing the game's theme before proceeding to break the picture frame in true Kerban fashion.