Cover for Head of a Dog; Tail of a Lion.
 
Fanfic summary:
 
“After being worked like a dog, Spike decides that the Princess Summit is for the birds. His trip to the market goes to the dogs when the Crystal Empire is subjected to an unprecedented raid on their home turf and Spike suddenly finds himself a bird in a gilded cage. It seems that birds of a feather flock together, though, and he is treated as top dog, so when his eagle eye spots some underpawed dealings, will he let sleeping dogs lie or will he beard the lion in its den?”