I suggest if you are suffering through a rewrite anyway that you move the data to tables where it belongs rather than hardcoding data into code. Join the existing table(s) to the metadata. Metadata in a table is reusable across multiple queries without the maintenance hassle of copy/paste. Data in a table is much easier to extend than finding all occurrences of a particular CASE. (suppose in this example you need to add the sound of a goat and there are a dozen CASE statements in as many SP using the animals table, and worse: ad-hoc command batches in application code)

I don't know what principle of data stewardship this notion espouses; I expect many long-time DBA would agree that the extra 15 minutes work to properly store metadata in tables will save hours of hunt&fix in the future.