Change Seats is a simple, indoor-but-slightly-physically-active game especially appealing to elementary-age children, but which can be modified to broaden its appeal somewhat. Change Seats works best with larger groups.
To play, designate a number of chairs that is one less than the number of players, and arrange the chairs in something like a circle.
The person without a chair calls out a category, directing all participants to find a new seat IF they fit into the category.
For example, the caller might say, "Change seats if you are...
...Older than 10
...Sitting next to an adult
...Born in an odd-numbered year
...a Disney fan
...Taller than their mother
Once the designated players start to scramble to trade seats, the caller attempts to take one of the vacated chairs. Whoever is left without a seat becomes the caller for the next round.
If only one person fits a category, then that person does not have to switch seats, and the caller must try again.
If a person who does not fit a category nonetheless erroneously attempts to change seats, then the safety of their seat is lost and they are treated as if they did fit the category.
If a person who does fit the category fails to change seats, the new caller may challenge that person. If the group agrees that the challenged person fit the category and should have changed seats, then the caller and the challenged person change places, and the challenged person becomes the caller.
If no very young players are involved, callers might try more sophisticated configurations, such as:
...Did not change seats last round
...Have the same number of vowels in your first and last name
...Are not seated next to someone with blue eyes
...Could not name the US Secretary of State
Callers are permitted to complicate the category by reversing the condition -- Do not change seats unless, everyone change seats except, change seats if X BUT NOT if Y.
Potential variations on the game would include an elimination version, in which a caller was eliminated from the game (and one chair removed) for calling an invalid category (fewer than two category members) or for failing to successfully re-seat themselves after calling a category.
A spin-the-bottle version for teenager-only crowds would allow the caller to retreat to the lap of a seated person, who would then have the privilege of kissing or rejecting the sudden tenant, with the suitor eliminated from the game if not kissed -- and one chair removed, with the rejecting person becoming the next caller.