Characters or pairings: Bill/Dennis Creevey Charlie/Dennis C, Harry/Dennis,
Scenarios:
1) Set in HBP, Bill might be engaged to a part Veela but she ca't fufull all his needs. Pretty, little (and Bill likes that Dennis is little) Dennis will do just fine for that however.
2) GOF, Charlie spots the kid who fell into the lake and didn't blink an eye. Small (probably tight) cute and up for anything. Charlie's type and he'll see how much Dennis can really take
3) Harry finds a Time Turner and for whatever reason goes back to summer before OOTP or HBP and befriend the Creeveys. Dennis in cutoffs and barefeet get to Harry, and Harry's never been good at resisting impulses. (Note, would not mind if someone was gracious enough to fill, then Harry in present time found Dennis and ao forth, or a hint of that)