I recently saw the "1000 things to do in a lucid dream!!!" post and really enjoyed reading it! Thanks moongrass! I really like the question how you could interact with a dream character.
What would you say to him/her? What would you talk about? ....
I hope this thread will get just as big as the other one, so feel free to post all your ideas!
I'll start with a few thoughts...

1. Tell him/her that he/she is only part of a dream
2. Ask what he/she stands for
3. Talk about your fears
4. Show him/her a magic trick and see what happens *hehe*
5. Send him/her on a mission to find something cool and see what he/she brings back
6. Tell him/her to do something awesome
7. Kill a DC?!
8. Ask one to join you on an adventure