The short begins with Dennis asking his parents, Mavis and Jonathan, if they could get a puppy. Mavis regretfully tells Dennis they can't and that raising a pet is a big responsibility. Johnny tries to intervene by suggesting they could get him a goldfish instead but before he can finish Dennis cries out in sorrow, transforming into a bat and flies away.
As Dracula is wandering through the hotel he notices Dennis sitting sadly on the ledge near the window. Dracula asks Dennis what's wrong and Dennis tells him that his parents won't let him get a puppy. Dennis quickly cheers up and asks Dracula if he could get him a Puppy. Dracula is hesitant at first but quickly gives in after seeing Dennis' sad eyes.
Dennis is seen playing with his toys with Johnny on the floor as Mavis reads a book on the couch. A knock is then heard at the door. Dracula opens up, but before he can speak, gets knocked into the room with extreme force, crashing into a wall. A gigantic blue dog bursts its way into the room panting loudly. Dennis' face lights up and jumps up to hug his new friend. Mavis looks at her father angrily but Dracula insists that every monster needs a good pet. Mavis looks over at the dog to see that he has had an accident. Mavis runs over in panic exclaiming "My living room!"
The following night Dracula is sleeping in his coffin when Mavis calls out asking him to look after Tinkle for them while she takes Dennis to school. Dracula groggily agrees and goes back to sleep. Immediately after Tinkle wakes up Dracula needing to go to the bathroom. Dracula takes Tinkle outside only for him to now be hungry. Dracula leaves and brings back a wheel barrel of meat but first requests Tinkle to do a variety of tricks before he can eat.
Dracula returns to the front desk where he continues to check in guests, growing increasingly annoyed by the giant dog behind him. A witch maid comes to Dracula and informs him of the skeleton family checking into the hotel. As the skeletons enter Tinkle rushes over to them to chew on their bodies. Trashing the lobby in the process. Mavis enters the hotel with Dennis and looks at the mess with horror, asking her father what happened. The short ends with Dracula sighing and telling the audience that he needs a vacation.
- Asher Blinkoff as Dennis
- Adam Sandler as Dracula
- Selena Gomez as Mavis
- Andy Samberg as Jonathan
- Joe Whyte as Tinkles
- Rose Abdoo as Witches
- The sixth Sony Pictures Animation short film to be rated G by the MPAA, after The ChubbChubbs!, Early Bloomer, The Smurfs: A Christmas Carol, Goodnight, Mr. Foot and The Smurfs: The Legend of Smurfy Hollow.
- The second Hotel Transylvania short film to be rated G by the MPAA, after Goodnight, Mr. Foot.
- Puppy! was (like Ice Age: Continental Drift with Scrat's Continental Crack-Up and Home with Almost Home, Ice Age: Collision Course with Cosmic Scrat-tastrophe, Despicable Me 3 with Mower Minions and The Lego Ninjago Movie with The Master) a short prelude to the film, Hotel Transylvania 3: Summer Vacation.
Puppy! has received positive reviews. Many film critics have said that the short was better than The Emoji Movie.