Artist and actress IU now has a new nickname under her belt: Endorphin.

On May 24, KBS released a string of photos from the filming session of drama "Lee Soon Shin."

Despite heavy-handed narrative currently taking place in the storyline, the actors and actresses seem to be keeping things light, according to their looks in the photos.

In the middle of positive, friendly filming environment stands IU, sources say. Acquiring a new nickname, Endorphin, IU has been praised from other cast members as well as the staff crew for her bright energy that sets a positive tone for the entire team of 'Lee Soon Shin.'

In the photos are IU's playful poses and childlike smiles in various locations.

The production company stated, "IU's constant smile and positive energy despite her incredibly busy schedule has been the biggest reason for the late push of our drama which is starting to garner more fans as we near the end."

Internet users have responded, "I am smiling just by looking at her smile," "These happy photos explain why the drama has best ratings," "She is doing exactly what a lead character should be doing. Fantastic."