Well, it is a baby puppy....over the weekend they went to a humane society in Naples Florida and adopted Shark, a French bulldog with some health problems.

Article:

https://www.naplesnews.com/story/news/local/2024/01/28/why-stranger-things-star-millie-bobby-brown-was-in-naples-saturday/72388192007/

Netflix 'Stranger Things' star, Bon Jovi's son adopt dog in Naples: What to knowNaples Daily News