Disclaimer: Dawn belongs to Joss Whedon, Ginny and Luna & the two behinds to J. K. Rowling.
Their eyes followed him from he swaggered past them until he turned at the corner. More precisely, their eyes followed his behind until it disappeared with its owner.
In their defense the behind was great, accentuated by a marvellous swagger. Anybody who spent that much time on a broom and the confidence of success, were worthy of a swagger like that. That they'd agreed upon during the first week of term. The trouble with that logic was that... oh. Yes.
"Weasley, Summers, Lovegood." This behind was accompanied by a sneer. A sexy sneer, they'd concluded. Who didn't like bad boys?