The Rock Star costume was a costume that came before the Rock Star 2 outfit. After this, the Poptropica creators redid the costume into Rock Star 2. They deleted the first Rock Star costume from the store. It came in pink, purple and green for girls, and white, blue and red for boys.
The Rock Star costume was replaced because the Poptropica Creators wanted to update each item one by one in Poptropica's early days.