My little cousins came over to be baby sat a while ago and saw me working on my Rarity costume, they asked if they could play ponies too. Now there's a chance they're coming to a con with me for a few hours as The Cutie Mark Crusaders if their mom has time to drive them there and back.
I've also had kids ask me if I was Sleeping Beauty when I was dressed as Jaina Proudmoore...I guess it's the blonde hair and the dress since these ones were very little. I didn't want to come off mean so I went with the 'sure, why not?' route and nodded.
Then one time I went to the mall during Otakon as Harley Quinn with my friends as Cat Woman and Poison Ivy. These women a bit older than us (so mid-late twenties) with toddlers said 'Aww! Batman girls! Kids, go take a picture with The Joker's girlfriend!' The little kids were terrified except for one so their moms just took pictures of my group and the one little girl.
"I did not spend centuries feasting on the souls of the righteous to play typing games with the functionally illiterate."-Kil'Jaeden, Scourge Chat Log #1