Give each person a paper doll (need not be fancy - just cut out of copy paper) or just a sheet of paper. Tell them to fold it as much or as little as they want, based on how the following comments on their job makes them feel.  Remind them that these comments are ones you have heard before (add your own) on your previous (or current) j.o.b.  Say these things with the same tone you would expect the boss or coworker to say it with:  

You can do better.
What have you done now?
You weren't listening.
You're not worth more money.
You have so much to learn.
You're making as much as you'll ever make.
You did fine... now I know you can handle more.
What are you going to do?  Look for another job?
That was stupid.
You don't have enough education.
We can't afford to let you take vacation.
You're too good at your job to promote you.
We need you... put your kids in daycare.
I've revised your goals for you.
Go ask the boss.
This is NOT a social hour.
Stop your daydreaming.

Now that their doll is in a tight little ball, read these comments to them.  Ask them to unfold as much or as little as they want, based on how these comments make them feel.  Remind them that these comments are ones you hear all the time in PL!  (add your own)  Say these things with enthusiasm! 

Great job!
Pick your reward!
Give yourself a raise!
You deserve it!
How about a vacation???  On us!!!
You have so much to teach!  Will you help train?
You earned it!
Set your own goals!
Get rid of the babysitter and spend MORE time with your kids/family!
You're your own boss!
Have fun!  Your life is a party!
We're proud of you!
Tell me your dreams...
You can do it!
If you want it bad enough, you'll get it!
Thank you!
I'm impressed!

Give a prize to the smallest ball/wad after the negatives.  Give a prize to whomever unfolds their ball first.  Each prize should be a sponsoring packet.