**Core Concept**
Methemoglobinemia is a condition characterized by an abnormal amount of methemoglobin in the blood, which can lead to tissue hypoxia. Certain local anesthetics can induce methemoglobinemia by metabolizing to compounds that oxidize hemoglobin to methemoglobin.

**Why the Correct Answer is Right**
The local anesthetic that causes methemoglobinemia is Prilocaine. Prilocaine is metabolized by xanthine oxidase to o-toluidine, which in turn oxidizes hemoglobin to methemoglobin. This is a well-documented side effect of prilocaine, particularly when used in high doses or in patients with certain genetic variants of the xanthine oxidase enzyme.

**Why Each Wrong Option is Incorrect**
**Option A:** Lidocaine does not cause methemoglobinemia. It is primarily metabolized by liver enzymes to glycine and pipecolylxylidine, which do not oxidize hemoglobin.
**Option B:** Bupivacaine also does not cause methemoglobinemia. It is primarily metabolized by liver enzymes to pipecolylxylidine and other compounds, which do not oxidize hemoglobin.
**Option C:** Mepivacaine does not cause methemoglobinemia. It is primarily metabolized by liver enzymes to p-isopropylpiperidine and other compounds, which do not oxidize hemoglobin.

**Clinical Pearl / High-Yield Fact**
When using local anesthetics, clinicians should be aware of the potential for methemoglobinemia, particularly with prilocaine. Patients with certain genetic variants of the xanthine oxidase enzyme may be more susceptible to this side effect.

**Correct Answer:** C. Prilocaine.