Gladiola is a generous, miniature, and pink poodle. He ran away from his home before the events of The Lightning Thief, but he was later found by the satyr Grover Underwood. He then agreed to be returned to his owner as a favor to Grover.
At first, Percy Jackson refused to say hello to the dog, but eventually agreed when Annabeth Chase pointed out that Gladiola was their ticket West. When Grover found him and talked to him, he told him about the $200 reward if he was found and returned, and agreed to be returned so Percy's group could use the reward to buy train tickets to go West. The dog is considered generous because he didn't like his home and ran away, but was willing to go back to help Grover, Percy, and Annabeth.