Can you please explain the bolded sentence?

Vic: Grandma, your house is magic. And the basement swallowed us up!

Victor: The wall art came alive!And all out stuff became a monster, and we burned him with green fire, and now everything's clean.

Grandma: Oh, I see. Whatever you have to dream up to learn to respect your Grandma's space.

Victor and Valentino, season 1, episode 6


"dream up" is imagine, or to make up some fantasy story..

The grandkids are coming up with many fanciful stories about the house.