“Let's burn that bridge when we come to it” – is this sort of idiom mixing considered a pun, and if so, does it have a specific name?
I couldn't come up with a short title, but the upside is that there is not much needed to be said in the body of the question! For @dmr (and others), it mixes “let's cross that bridge when we come ...
Assume we have a literary masterpiece that is abundant in symbolism and metaphors. Within this masterpiece, the author uses a brook running through a glade of trees to represent a couple of things ...