Either it's just run-of-the-mill that a hospital would have a serious inventory of pigs or someone in the props department found one left over from a few seasons ago and was like, hey, you know what was cool? When the students had to save pigs' lives as a learning exercise! Let's give one of those little guys another shot at fame! Alex is practicing for his surgery when Cristina walks in and tries to take the pig from him but he is the first in a long line of people to ask Cristina if pigs really do have appendixes. (Dr. Google tells me no, they do not.) Mere runs in and offers up her aneurysm but she has no takers; Cristina is too caught up in her panic as she tries to remember how to do an appendectomy, since she hasn't so much as thought about one in at least three years. Mere keeps begging since she's freaked out about how Derek is going to act but no one else wants the crazy risky surgery for their first time out of the gate. Jackson runs in and requests just the pig's head for some practice of his own, and then April joins her disobedient charges to try and ask Alex to talk to Jason before his dad's surgery. Alex instead orders her to kill the lights and shows off the neato surgery he just did: injecting the bowel with glow-in-the-dark dye that you can see under a black light. Any piece that is viable will light up like the Main Street Electrical Parade. After they gaze, transfixed for a moment, the residents all scatter. Cristina realizes that there is a skills lab going on and makes a beeline for the interns. April tries again but Alex yells at her that answering questions isn't his job. Actually, isn't that completely and utterly part of his job? I am not sure when it became that surgeons don't have to talk to patients with questions about their surgery. Isn't that part of the definition of being a doctor, in fact?
Cristina runs into the skills lab and asks the interns how many of them know how to do an appendectomy. She is pleased and practically starts twirling her moustache and tapping her fingers with a cackle like an old-timey villain.