The Douyin special effect you described is "Do you want to add green onions", which is a relatively popular special effect recently.

This special effect is usually used when using recipes or food preparation processes, and it will have some humorous and exaggerated elements.

If you want to use this special effect, you can follow the steps below: 1. Open the Douyin app and select the video to which you want to add special effects.

2. In the interface for shooting, editing or uploading videos, find the "Special Effects" button, and then select "Edit" or "More".

3. Search for the special effect of "Should I add onions?", which can usually be found under the "Gourmet" or "Funny" categories.

4. Select the special effect and apply it to your video. You can adjust parameters such as position, size and duration as needed.

5. Preview and save your video and share it with friends or post it on Douyin platform.

It should be noted that the use of TikTok special effects may be restricted by copyright, trademark or other legal regulations. It is recommended that you comply with relevant laws, regulations and platform regulations to avoid infringing the rights of others or being processed.