Which of the following is an example of metathesis?

Metathesis is a linguistic phenomenon where sounds or syllables in a word are rearranged. The example of "spaghetti" becoming "psketti" illustrates this concept clearly, as the initial sounds 's' and 'p' are switched. This rearrangement alters the pronunciation while retaining some recognition of the original word, showcasing how metathesis can impact language through playful alterations.

In contrast, the other options do not represent metathesis. The reference to "Kleenex" indicates a generic use of a brand name for a broader category of products, known as generic trademarking rather than a sound change. Similarly, the shift in meaning of "cool" shows semantic change rather than phonetic alteration. Lastly, defining "dog" as a specific breed is a narrowing of meaning within semantics, not a phonetic rearrangement. Therefore, the correct identification of metathesis aligns directly with the sound alteration seen in "spaghetti" becoming "psketti."