The dish the student ordered is no longer available. The server must suggest an alternative — the student has to react and decide.
The server accidentally brings the wrong dish. The student has to politely point out the mistake and ask for the correct one.
The server asks an unusual question, e.g. "Would you like to try our new seasonal special, it's not on the menu yet?" — the student must respond naturally, not from memory.
At the end, the student needs to ask to split the check between two people.