**Core Concept**
The patient is experiencing a neuroleptic malignant syndrome (NMS), a life-threatening disorder caused by an adverse reaction to antipsychotic medications, particularly typical antipsychotics like haloperidol. NMS is characterized by a combination of symptoms including fever, muscle rigidity, altered mental status, and autonomic dysfunction.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with NMS, which occurs due to dopamine receptor blockade in the central nervous system. Haloperidol, a typical antipsychotic, blocks dopamine D2 receptors, leading to an imbalance in the dopaminergic system. This imbalance results in excessive stimulation of the brain's motor control centers, causing muscle rigidity, and autonomic dysfunction, manifesting as tachycardia, labile blood pressure, and leucocytosis. The increased CPK enzyme levels indicate muscle damage and leakage of intracellular contents into the bloodstream.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because NMS is not associated with serotonin syndrome, which is a different condition caused by excessive serotonin activity in the central nervous system. Serotonin syndrome is characterized by symptoms such as agitation, confusion, and autonomic instability, but it is not typically associated with muscle rigidity or increased CPK levels.

**Option B:** This option is incorrect because malignant hyperthermia is a separate condition caused by a genetic predisposition to an abnormal response to certain anesthetics, such as succinylcholine or volatile anesthetics. While both NMS and malignant hyperthermia can cause fever and muscle rigidity, they have distinct underlying mechanisms and are not directly related to antipsychotic medication use.

**Option C:** This option is incorrect because neuroleptic-induced parkinsonism is a common side effect of antipsychotic medications, but it is not characterized by the same severity of symptoms as NMS. Neuroleptic-induced parkinsonism typically presents with bradykinesia, rigidity, and tremors, but it does not involve fever, autonomic instability, or increased CPK levels.

**Option D:** This option is incorrect because serotonin syndrome is not directly related to the use of lithium and haloperidol. While lithium can cause serotonin syndrome when combined with other medications, the patient's symptoms are more consistent with NMS due to the use of haloperidol.

**Clinical Pearl / High-Yield Fact**
NMS is a medical emergency that requires immediate recognition and treatment. The diagnosis is based on clinical presentation and laboratory findings, and treatment typically involves discontinuation of the offending medication, supportive care, and symptomatic management.

**Correct Answer: C. Malignant neuroleptic syndrome**