Even though they doze 18 hours a day, Thursday –– or, what was left of it –– was a big date for Tekin and Kobi, the two koala bears on loan to the Dallas Zoo from San Diego. Once a year, they join all the other zoo animals for a critically important health checkup. It’s a lot like a human physical, except the marsupials are under anesthesia for everyone’s safety. “I wouldn’t be able to check their teeth or anything like that, not without getting bitten,” said Dr. Geoff Pie, senior veterinarian at the San Diego Zoo. “They have a very nasty bite.” There are 10 people making sure the exam, blood pressure, X-rays and blood draws and performed quickly and efficiently.