D.R.
Hi P.,
We are having the same problem with our 3 1/2 year old son. I took everything out of his room except his bed and dresser. I told him when he started going down for naps and bedtime like a big boy again then we would start putting things back in. That worked for naptime but at night he kept running out of his room laughing. We tried putting him back into his bed without saying a word but that didn't work. We started threatening that he wouldn't be able to do certain activities, such as going to the Children's Museum or the library (whatever was on the schedule for the next day). We told him he had to go to bed or he would be too tired to go anywhere. We also woke him up at regular times in the morning and after afternoon naps. This was hard for him because he was getting to sleep so much later. With all of that he is finally starting to get better. He has stayed in bed the last three nights. I keep reminding myself someday we will be yelling at him to get out of bed at noon!
Good luck!