Fleas bite, and their saliva is very allergenic to susceptible animals. This causes skin redness, itching, biting, scratching, chewing, crusts in the skin, and even a greasy feel and strong odor for some pets. In non-allergic pets, fleas don't bother the animal in these classic ways. Fleas love humidity and warmth.
It is a way of getting their name in the tabloids to promote their latest movie. Andrew Garfield likely got a text message, from his agency, informing him that he was dumping his girlfriend and on which date the media would break.
Andrew's (Ryan Reynolds) parents have a pet dog named Kevin. Several American Eskimo/Samoyed puppies were alternated in this role and were rested between takes. Streets were closed off to traffic and grounds were inspected for safety before filming. Cast and crew members were introduced to the dogs and instructed on their proper handling.