Reportedly flying around the cabin amidst screams on a recent flight from Madison, Wisconsin to Atlanta, Georgia was a bat. It flew around the cabin several times on Delta Connection partner Atlantic Southeast Airlines flight 5121 before being trapped in the lavatory at the rear of the aircraft. The flight was then diverted back to Madison.
Included in the DL 5121 diverted last friday due to bat thread is a link to actual video of the incident.
Perhaps the bat was conserving its energy by being a passenger on an airplane instead of flying on its own power to its destination?