f(x) has stirred up some controversy related to behaviour and mannerism again.
This time, the attention was focused on Sulli, who was clutching the hem of her skirt instead of dancing to 'Rum Pum Pum Pum' during f(x)'s performance on September 11.
The girls were on stage for the World Federation of Neurosurgical Societies symposium, reports AllKpop.
Netizens pointed out that she failed to do the part of the dance where the girls lie on the ground then push themselves back up.
In the pictures, Sulli is just squatting down while holding her skirt. People are saying she is not trying her best and criticising her online.
One said, "She has neither the energy nor the drive. Far from giving fun and energy to the audience, it feels like she is taking them away."
Another said, "Maybe Sulli really is not meant for the idol life as she doesn't seem like a pro the way she always surprises people with her attitude."
Others have defended her, saying it might be due to her sudden diet plan, or perhaps the skirt was too short and she just felt embarrassed.
SM Entertainment defended her, "It appears that Sulli failed to follow the choreography because she was not feeling well at the time."