Simplify the following text for a Grade 5 native English-speaking person.
Original: Barbie was one of the first toys to have a marketing strategy based extensively on television advertising , which has been copied widely by other toys . It is estimated that over a billion Barbie dolls have been sold worldwide in over 150 countries , with Mattel claiming that three Barbie dolls are sold every second .
Simplified: There have been many other dolls like Barbie since Barbie was first produced .