Here's why:
* "One Night Only" is a popular song title: Many artists have songs with that title. You need to specify which song/video you're asking about.
* Emma Watson's career: Emma Watson is primarily known for her acting career, but she's also involved in other projects.
* Music video appearances: It's not unusual for actors to make appearances in music videos, but you'll need to provide more information for me to know if she's in the specific video you're thinking of.
To get a helpful answer, please tell me:
* The artist who made the "One Night Only" song.
* The year the video was released.
Then, I can help you determine if Emma Watson is in it!