Don't Tell Mrs. Patel... Yikes

In "Escape from New York" from "Resident Alien," Dr. Smallwood accidentally mixes up Mayor Ben Hawthorne's file with that of a woman named Mrs. Patel and tells him that he has an aggressive form of colon cancer. Before he can really process this, Nurse Ellen Cho shows up and explains that Dr. Smallwood mixed up the files. Dr. Smallwood says that this happens sometimes. "Should it?" asks Ben, pointedly. "No," deadpans Ellen.

Example of:
File Mixup