In American works, using the metric system is viewed as "fancy" or "posh."
Americans normally use American Customary Measurements in everyday life. However, the metric system is far from unknown there, as it's often used in scientific publications and naturally in media from other countries that use metric. Particularly the former, however, leads to using the metric system being viewed as "fancy"; it's what them fancy scientists use, after all. This combined with its association with Europe (where a large chunk of non-American media that Americans consume comes from), which is often viewed as fancy in the US as well, creates the impression that use of metric is posh. As a result, characters such as the Insufferable Genius will often use metric measurements in American media. Ironically, in many parts of the world where metric is the standard, the reverse is actually true, with Imperial measurements being viewed as "fancy" or "posh," but in the same sense that using Flowery Elizabethan English is viewed as such. Seen It a Million Times