Crookshank was a seeker (well, maybe that is)

[stlcole]

No: HPFGUIDX 67600

I don't know if there is much discussion of Crookshank .. I really 
haven't figured this caracter out, other than to suspect that is not 
simply an animal (most likely a kneazle) .. but when Harry brought 
back the snitch from the OOP quidditch match v. Slytherin into the 
common room, Crookshank chased the snitch around the room:

chapter 19, pp. 417: "The Snitch he had caught earlier was now 
zooming around and around the common room; people werw watching its 
progress as though hypnotized and Crookshanks was leaping from chair 
to chair, trying to catch it."