Conversation so far:
When was Katy Perry's first album under her stage name?
03/06/2001
What did Katy Perry do between 1999 and 2001?
In Nashville, Katy Perry started recording demos and learned how to write songs and play guitar.
Was her first album as Katy Perry a hit?
While Katy Hudson received positive reviews from critics, it was commercially unsuccessful and sold an estimated 200 copies before the label ceased operations in December.
When did Katy Perry start gaining commercial success?
Katy Perry had minor success prior to her breakthrough. One of the songs she had recorded for her album with Ballard, Simple

Question: What was it that started gaining her popularity?
Self-contained rewrite: What was it that started gaining Katy Perry's popularity?