I used to have a springer spaniel that would jump a 5 foot fence every day to go sit with my neighbors kids in the afternoon and watch TV. When it was time for them to eat dinner he jumped the fence again and came back home.
Our neighbor's dog used to come over and sit by the turkey pen for company. One time, as far as we could tell, she picked up our pet rooster and carried him back to her yard. He reappeared the next afternoon, perfectly unhurt but a little confused.
A very fat Labrador retriever greets every picnic and barbecue party that visits the small park adjacent to his oceanfront home in yellow point on Vancouver Island. If you visit here and see that dog don't feed him. He's too damn fat
I have a cat that shows up everyday for a similar reason. He lives with a 2 dogs (one a puppy), and 3 kids. He just needs a little time on someone older and calmer's lap/couch.