Mrs. Lightfoot uses water spray to discipline Blazey, which may also be useful if the dragon accidentally sets something on fire.
People in this universe live in mushroom houses and have fire-breathing dragons as pets. Mushrooms are highly flammable, so house fires must be common...
Unicorns being the equivalent of pests may be Played for Laughs, but remember unicorns are shown to have bigger body than real world pests like raccoons and rats. In other words, has anyone in this world been bitten or severely hurt by these large size unicorns? And what other Large-size magical creatures are considered pests?
Add to this that they have long, pointy horns. An aggressive unicorn can easily impale a person.
Which is what unicorns were known for doing to people before Disneyfication.
The mermaid sitting in a kiddie pool in the front lawn. How in the world did she even get there?
A legged friend, relative, or life partner could have carried her there.
Mermaids may move around on land similarly to a wheelchair-bound person.