The commander pulls an April Fools' Day prank on the crew – Commander's Report: lunar day 2

Commander Musilova pranked the new Selene V crew with the help of a previous crew at the HI-SEAS habitat, as part of their initiation to surviving their analog lunar mission.

Source : https://www.space.com/hi-seas-selene-v-moon-analog-mission-commander-report-1