One example of an early "dance" was the Boss Walk. This one is almost completely gone now but it was essentially an inside joke to people who followed the content of the platform.
Another thing special to TT is that it was successful at sucking content in from other platforms, including Instagram, and then having that be remixed via the audio under unclear licensing terms. A good example of this is the "oh shit it's a rat" meme.
Once the meme makes it into the blood of the userbase, it doesn't even need the audio and it can take on a life of its own leaving behind most content origination though the audio stays.
The most impactful example was definitely Old Town Road, and the jump / costume changes. This song was huge on the platform and already waning before it made it onto billboard and exploaded mainstream
The real killer is the dances on the music. They don't have to invent a new topic every time. They just see a music video they like, and imitate it. Together with all the effects it's very easy to create a crazy video with basically nothing.