These dances should be walked thru before being called. The dancers will have the opportunity to see how the figure works. They will then have a higher level of success in performing the dance. Part of the procedure should be an understanding between that caller and the dancers that the caller will not expect the dancers to remember how to dance the gimmick figure after the party is over.
A good example of such a gimmick is a old figure that was popular for a time about 20-25 years ago called Who's On First. It is a take off on the old Laurel and Hardy routine about baseball.
As the routine progresses, different people are in 1st, 2nd, 3rd and 4th positions in the square. It makes the people think a little and usually produces a lot of laughter as people scramble around and try to remember where they are.
From a static set, on the call of Who's on First, the #1 couple walks across the set into the #3 position and does a U-turn Back. As they are doing this, every other person in the set slides one position (1/8) to the right or to the left. Everyone is now in a new position.
Now call Who's on Second, and the new #2 couple crosses the floor to step into the #4 slot and U-turn Back. The routine proceeds with Who's on Third and Who's on Fourth and then repeats with Who's on First and Who's on Second again.
The routine call also easily be called directionally or with a combination of both. For example. You could call.
Who's on First ... #1 Cross the set & U-turn Back.
Who's on Second ... new #2 cross the set and U-turn Back and so on.
Any six consecutive numbers will result in the set being back in order in a static square. This means if you start with #2 then you proceed to #3, #4, #1, #2, #3. Problem point - On the first , third and fifth times the square will end up with everyone in 1/2 sashayed position. The couple going across the square will sometimes attempt to put the lady back on the right hand side rather than doing a U-turn Back.
Any three consecutive numbers will result in a setup with everyone with the opposite person and in 1/2 sashayed position. A getout from here could be Heads Pass Thru & U-turn Back ... Side Pass Thru and U-turn Back ... All Four Ladies Chain ...
Another way to add variety is to work around a theme that is different, but still doesn't require the use of new terms that the dancers must remember. A good example is a directional call to put the ladies or the men in the center back to back. While it is a good idea to quickly demonstrate the idea, the dancers will recognize that it is something to be enjoyed for one dance and the next time it is used they will be re-introduced to the concept with another quick walk-thru.