Have you met Karli? Her mom struggles with substance abuse, and she is in foster care. Karli is not a real child…she’s a six-year-old Muppet with yellow pigtails made of ostrich feathers. The creators of Sesame Street introduced her on the show last month. They did it because more than 400,000 children are in foster care in this country, and it is estimated that nearly 80% of those cases involve substance abuse.