What are some virtual worlds for 4 and 5 year olds?

So I'm babysitting my baby cuz, Lilly. She wants to "make accounts" (as she calls it). In her world apparently, to "make accounts" is to make virtual avatars. We tried barbie.com but it was closed down, and I don't want to try moshimonsters.com because I heard people track you down and do bad things, and she's only 4!! And things like clubpenguin.com and poptropica.com are too old for her. She's getting really unpatient, so can you help me fast? Thanks!