I love my little trick or treaters! I made them a couple of years ago and this is how I did it. You take a foam ball about 12 inches big and hot glue two wooden dowels into it. I just kept pushing and twisting the dowels until it dug a hole. Then I took the dowels out, filled the holes up with hot glue, and put the dowels back inside. I held them in place until the glue was dry. Then I bought a white flat sheet and cut two big circles out of it.
Then I hot glued the middle of the sheet circle cut-out to the top of the ball.
Then I hot glued two black felt ovals for eyes to the front of the sheet.
Then I put some little jeans over the two dowels.
I purposely wait to plant flowers in my pots out front until Halloween is over so I can put my little trick or treaters in them. So either in your grass or as in my case the dirt of the pots, push the dowels into the ground until it feels secure.
Then take newpaper or mail and crumble it into balls and stuff the pants.
I always add a bow to one of them so that it looks like a boy and girl. I safety pin little treat bags to their side. I also safety pinned the sheet to the jeans all the way around because I got sick of the wind blowing the sheets around.