The phrase "we got us a spy" can be viewed as an example of colloquialism. Colloquialism refers to informal language that is often specific to a particular region or group, and it captures the natural speech patterns of everyday conversation. This phrase uses informal grammar and syntax, with "got us" being a less formal way of saying "have."
Additionally, if the context implies surprise or emphasis on the discovery of a spy, it could also be seen as an example of idiomatic expression, where the phrase conveys a meaning that might not be understood from the individual words alone.
Without more context, it's challenging to determine if there are other literary devices at play, but colloquialism is the most prominent device here.