The FOX News article is terrific, and is packed with historic details:
In the hours before Discovery's liftoff, NASA's Final Inspection Team (called the "ICE team") investigated whether the creature would pose a risk to the shuttle if its body impacted the orbiter's sensitive heat shield tiling. Ultimately, NASA officials signed a waiver confirming that the bat was safe to fly with.
"The bat eventually became 'Interim Problem Report 119V-0080' after the ICE team finished their walkdown," the memo said. "Systems Engineering and Integration performed a debris analysis on him and ultimately a Launch Commit Criteria waiver to ICE-01 was written to accept the stowaway."
This isn't the first time a bat has attempted to travel into space. Another bat was seen clinging to the side of the external tank attached to the shuttle Endeavour on its STS-72 flight in 1996. That one maybe have been a bit more cautious, though: It flew away to safety right before launch.
Coincidentally, an astronaut aboard that flight, Koichi Wakata of Japan, also flew on Discovery this week, making him the first spaceflyer to share two rides with bats.