If Mettaton had a choice between busywork and watching J work...well, he'd take the second option. The curious look doesn't put him off, especially not when the young woman does her flirty twirl. Ooh, she's good! Well--she was already ace before he came in here.

But her showmanship is excellent, and although he can't really join her, his damaged grid manages to flash out a bright heart of appreciation.

"Oh my, having fun, are we~?" he hums. If he was in his other form, the flirt would sound less creepy, probably. Just...let him have this, J.