The SocialJigTwoPerson glitch is a glitch in The Sims 3.
After installing an expansion pack (most notably University Life or Supernatural), gray ovals may appear in the ground in a saved game that was created before the pack was installed. Sims will not be able to walk on them, furniture can't be placed on them, and they can't be moved in Buy Mode because it claims that the object is in use.
When the MoveObjects cheat is used to relocate the ovals, their name will display as "SocialJigTwoPerson" and they can be deleted.
No real information is currently available, but it is speculated that the glitch is caused by a reset during an interaction. Whenever Sims interact, a small area is created that other Sims can't walk through. If they are somehow reset, that untouchable area might stay there even though the Sims aren't.