It feels good to get out of the museum for a night.
A human couple might consider going to the museum for a night to be an exciting date night. Here, the mummies, who usually reside in the museum (e.g., the history museum's egypt section), have the opposite perspective: for them, it feels like an exciting date night to get out of the museum for a night and be normal people in a normal house. It's funny that a human couple and a mummy couple could switch places (home/museum) to both have exciting date locations.