Not the sort of occasional vague resemblances that we so commonly see. Distinct, clear, and unmistakable. Hamlet's "Very like a whale." line would be impenetrable, because while they do have cloud that look like whales, weasels, and camels, they could never be confused.
Local color, I thought, but then, I thought, it would affect the world-building in more serious matters. A light-hearted, brightly colored world allows some themes, some plots, some world-building, but not others.
Variation is allowed. In fact, it's required. Only a very short story can keep on the same level of seriousness all the time, indeed stories often need to build in seriousness, but still it needs to keep within a certain range and pushing too far can break the mood. A madcap and humorous caper story can rise to real danger, but a grim and gritty depiction of a death doesn't fit -- just as having the desperate deserters from a broken army in a grimdark tale stumble on a non-ironic Big Rock Candy Mountain will kill the story through mood whiplash.
The delicate part is figuring out what mood whiplash is story killing rather than dramatic. Mulan was a very -- uneven film, but one of the great moments is when the soldiers were caroling along about girls and stumble on a battlefield. Of course, the stakes had been settled very early in that film, and the battlefield was not gristly. . . .
On the other hand, one of its flaws was scenes where the whiplash was too great. We have the marvelous, grave, silent departure from the house in the dead of night, and the ancestors appear like a cloud of buffoons. And produce the ridiculous dragon. That was from the sublime to the ridiculous, and it was too much.