The star lauded contestant Jena Irene's performance as "phenomenal," but said Irene could have been "more messy."
"Do you know what I mean?" Lopez asked as she flipped her own hair around wildly. "You were kind of fixing your hair, and right at the beginning you kind of just threw yourself into the crowd and your hair went crazy. I wish it would have been more messy."
Fellow judge Keith Urban asked Lopez to repeat the move as a joke, which caused Harry Connick Jr. to chant, "Hair flip! Hair flip!" Lopez dropped the F-bomb on live TV in response to Connick's goading.
"That's Jenny from the block!" Connick announced immediately afterwards as he burst into laughter. Lopez had covered her mouth in shock after she uttered the curse, but decided the best move was to just continue the critique. Connick continued to crack up as Lopez finished giving Irene pointers.