Apollo 10’s lunar module was named Snoopy during its rehearsal for a Moon landing.
Apollo 10 launched on May 18, 1969, with Thomas Stafford, John Young, and Eugene Cernan aboard. The lunar module Snoopy descended to about 15 kilometers above the lunar surface while Stafford and Cernan practiced the procedures needed for landing.
The command module was named Charlie Brown. After separating from the command module, Snoopy performed the descent and ascent portions of the rehearsal, then rendezvoused with Charlie Brown in lunar orbit. This made Apollo 10 the final full dress rehearsal before Apollo 11.
Snoopy was not a random nickname: NASA and the crew selected names connected with the Peanuts comic strip. Apollo 10 did not land, and its lunar module ascent stage was later sent into a heliocentric orbit rather than being deliberately crashed on the Moon.