She really tries not to grin at the thought, or the mental image that brings up. But it's a losing battle.

Her lips twitch slightly from the effort of holding it back, and then she just breaks into a peal of laughter. "Erza did that!?" Oh Poor Master, a leprechaun. And then she slumps on the table with her hands over her head, still laughing.

"Oww - I shouldn't have done that --" But that was really really hilarious and well worth that smallish headache.