Avatars can sit on objects and the ground. Avatars cannot sit on attachments. (One way to fake this would be a separate object that “followed” the target avatar using a sensor and llMoveToTarget, but there would be a noticable delay when the other avatar moved.)
Sitting on an object causes the avatar’s mass to be added to the object.
|llAvatarOnSitTarget||Returns the key of the avatar sitting at the current sit target.|
|llSetSitText||Sets the Sit text on the pie menu.|
|llSitTarget||Sets the position the avatar will sit at.|
|llUnSit||Forces a sitting avatar to stand up.|
changed: raised (with the CHANGED_LINK flag) when an avatar sits/unsits on an object.
Q: How do I force an avatar to sit on an object?
A: You can’t. You can only force them to stand up. It is possible to animate an avatar so they look like they’re sitting, but not to control their position with much precision or reliability, at least not without using attachments.
Q: How do I find out the key or name of the object a given avatar is sitting on?
A: The short answer is, you don’t. In theory, you could do something with sensors, but this could return many, many false positives.