I encountered thsi trick quite recently so hopefully not too many people will know it.
First I will start a number and the next poster look at it and put the first number that comes into your mind (they must be positive integers between 1 and 1000). Then the next person and the next person etc. Soon a chain will build up but also a pattern - I will post the connection once a few numbers have been posted and you will be shocked at how you missed it.

Ok, so here is the starting number - 535.

718

412

20

(which also means the pattern isn't that they will all usually have three digits?)

333

332

971

64

535

541

Originally posted by crazyblue
541

Originally posted by wolfgang59
657

Originally posted by strokem1
821

Originally posted by Roosty
268

97
wow, so many odd numbers...