Complex sentence: A new co-worker, Tina Molinari (Nancy Lane), joins Rhoda and Jack at the costume shop, having appeared in several Season 4 episodes as an employee at Gary's jeans store.
Split into simpler sentences: A new co-worker, Tina Molinari (Nancy Lane), joined Rhoda and Jack at the costume shop. She had appeared in several Season 4 episodes as an employee at Gary's jeans store.