Riley is a stray mutt in Homeward Bound II: Lost in San Francisco, and the leader of a gang of stray dogs.
Riley is the leader of a gang of street dogs, whose names are Delilah, Bando, Sledge, Stokey and Spike. He is first seen arriving with his gang and saves Shadow, Sassy and Chance from Ashcan and Pete. He then tells Shadow and Sassy (Chance fled, thinking Riley's Gang were reinforcements) that it is unsafe to be around here because there are humans present, and humans are bad news.
Riley reveals that he hates all humans, as well as pets who associate with humans, Delilah tells Chance that when Riley was a puppy, he was a Christmas present for a boy a long time ago, but the boy refused to play with him and like him, the parents got rid of him by leaving him in a gutter on that Christmas night in the rain. He starts to change his mind after Shadow rescues a boy named Tucker from a burning house. When he asks Shadow if a human would risk their life to save him, he tells Riley that his owner Peter would. He then agrees to escort Shadow and Sassy home. However, Riley isn't pleased when he sees Chance hanging with Delilah (they had sparked a romance together while he and his gang had left). Indignant, he tries to convince Delilah that she shouldn't be with Chance because he is a housepet. She refuses to listen to Riley at first, but when Chance's unruly antics get him and Riley's Gang in trouble, Delilah reluctantly dumps him, causing Chance to storm off heartbroken.
Riley and his gang attempt to find Chance, but to no avail. Riley is last seen leading Shadow and Sassy to the bridge, where he and the two housepets prepare to go their separate ways. Before they do, Riley tells Shadow that he'll keep in mind about what the golden retriever said about humans, to which Shadow replies, "Riley, you're all right." Presumably, he also allowed Delilah to quit his gang to be with Chance.
- He shares a similarity to Buster and Shere Khan in that Buster hates pets who associate with humans, and Shere Khan just hates humans in general, so they have always had a hatred for humans. This is known as misanthropy. The only difference is Riley is not a villain.