I pulled this one on my daughter. She had a lose tooth, and wanted me to help her get it out. When I reached for it, I could tell how nervous she was.
"I'll go one, two, three, pull! Okay?" and she nodded. "One," YANK "..two three pull." She stared at me and said - "That didn't hurt at all!"
Pain is often a learned response, and for many years I tried to keep her from learning it. This backfired, of course, when she once held up a broken arm and wiggled it back and forth in my face. "See daddy? It doesn't hurt!"