This term refers to the video description box on YouTube.
This box, which contains information about the video, links, and tags, used to be universally referred to as the "sidebar," since it often appeared beside videos, but Craig Benzine (Wheezy Waiter) started referring to it as the "doobly-doo."
Other YouTubers, such as John Green (part of the Vlogbrothers) and Dan Brown, started to also call the sidebar the "doobly-doo," using Wheezy Waiter's terminology (and crediting him in various comments and tweets). The term is now widely used on YouTube.
This definition is designed to correct and expand on the definition 'dooblydoo' (misspelled) currently on UD
For more information, the link's in the doobly-doo.
To vote for me, please click the link in the doobly-doo.
The description section on most youtube videos.
Youtuber: All right thanks for watching guys, and the link is in the doobly-doo.