What's the worst that could happen?

The humor in this meme comes from the irony of the situation - the assumption here is that the wolf would not have come over to the fire to get some food if he knew that they would have dressed his ancestors in silly flower hats as a result of his actions.

Dogs dressed in flower hats by itself is a pretty funny image, honestly. It is rude to dress animals up in clothing because the animals generally don't like it (except for clothing that is functional, like a warm coat for a short furred dog for use outside in the cold), but people think that it is cute, so they do it anyway.

This is also a but absurd, because I imagine that the wolf wouldn't have cared that its ancestors would be dressed in flower hats - it probably couldn't even understand the concept.