In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.

Sentence1: Dennis decides he wants more hours at work. Sentence2: He decides he doesn't want to ask his boss for more hours. Sentence3: So, instead he just dawdles at night before he clocks out. Sentence4: But his boss is taking notice and tells him to stop. Sentence5: Dennis decides to ask his boss for more hours.
Dennis, Boss

Sentence1: I used to deliver fliers everyday in the hot sun. Sentence2: My water bottle always ended up really hot. Sentence3: When I put ice in it, the ice melted. Sentence4: I decided to buy a special thermos that kept the cold in. Sentence5: Now I always had cold water when I was in the hot sun.
I (myself)

Sentence1: Mary adopted a dog from an animal shelter. Sentence2: The shelter requires the adopted dogs to be spayed or neutered. Sentence3: Mary procrastinated because she was afraid about the spay surgery. Sentence4: The vet told Mary the operations are very common and not to worry. Sentence5: The dog had the surgery and is doing very well.
The dog, The vet, Mary