We had our elf come for the first time last year, the day after Thanksgiving. That was the day/evening we started Christmas decorating so I thought it was a good time for him to make his appearance. About a month before I started talking about elves, how we might get picked this year to have one visit us etc. My boys were 7 and 3 1/2 and they both loved it! He came with a letter from Santa, stating how the boys were to come up with and agree on a name for their elf. His name is Candycane (because he has little candy canes on his elf hat) Toymaker. He caused all kinds of mischief last year and my dh was about to send him packing back to the North Pole! The boys know not to touch him, they can hold him briefly/give him a kiss goodnight but he normally stays in the spot where they find him in the morning.
The boys found out that the elf has green pee, since he got it on the bathroom floor and didn't flush the toilet. He tried to make muffins one morning but left the egg shells in the batter and he left a note saying he didn't know how to cook them so he gave up. My MIL was living with us last year (and she said that was her best Christmas ever, watching the elf and the boys each day) and one night the elf took her car to McDonalds-parked it very much the wrong way in the driveway, had pillows on the seat and a couple stuffed animal friends helping with the pedals, he left happy meal wrappers and drink cups all over the floor but a note saying if the boys helped him to clean it up they would find something special in the glove box which were two gift card for McDonalds. That was the funniest thing he did and the kids got a huge kick out of it. Since my MIL lives right down the street now, I think the elf will continue the tradition of taking her car out joy riding to the fast food joints in the middle of the night. Oh, I should have him leave the car in our drive way though! The elf took green and red streamers and threw them around our ceiling fan in our room and took my ds's stuffed animal for a ride on it. He was found in the freezer, in the washer and dryer too. He even went out and bought two small christmas trees and ornaments, decorated them and placed them in the boys' room along with a little webkinz. We woke up Dec 24th to a tp'd downstairs! My dh I think was going to have me committed or something when he saw that. But the elf just had to do one last mischievous thing before he left the next night. After christmas last year I bought a lot of stuff on clearance to use for him to leave the kids little things at night.
I got way too into this last year and my dh is really hoping Candycane Toymaker doesn't show up this year until Christmas Eve, when it's time for him to go back with Santa! I would sometimes forget to move him to a new place at night before I went to bed. So I'd jump out of bed and go run around trying to think of some where new to put him. I just wish I had learned of this years ago. It really made our Christmas extra special last year and I hope I have a few more years where my kids truly believe!
There were times I'd go to bed and then realize he was still in the same spot as that morning so I'd jump up and just move him to a new room as I was too tired for him to be mischievious that night! The kids had an absolute blast each morning, often before 7am, running around with my MIL (who lived with us last year) trying to find the elf and find out what crazy thing he did durning the night! That's why I kind of want to start the day after Thanksgiving again, it's so much for them. 
