| Clue | Source | Date |
|---|---|---|
| Knock response | LA Times Daily | 04 Aug 2019 |
| Knock response | The Washington Post | 04 Aug 2019 |
| Knock response | ||
| Response to 'Knock knock' | New York Times | 26 Jul 2017 |
| Response to "Knock knock" | ||
| Response to the sounds at the ends of the starred answers | Wall Street Journal | 06 Sep 2016 |
| Question to a jokester | Wall Street Journal | 31 Mar 2016 |
| Obligatory joke response | ||
| Obligatory joke response | ||
| Response to 18-Across | ||
| Knock-knock question |