**Core Concept**
Catatonic schizophrenia is a subtype of schizophrenia characterized by marked motor disturbances, including immobility, rigidity, and mutism. It is often associated with a catatonic triad of symptoms: immobility, waxy flexibility, and negativism.

**Why the Correct Answer is Right**
Catatonic schizophrenia is a distinct clinical entity within the schizophrenia spectrum. The characteristic symptoms of catatonic schizophrenia include immobility, where the individual remains still for extended periods, waxy flexibility, where the individual maintains an uncomfortable position for an extended period, and negativism, where the individual resists or refuses commands. These symptoms are thought to be related to abnormalities in dopamine and serotonin neurotransmission.

**Why Each Wrong Option is Incorrect**
**Option A:** Hallucinations and delusions are common symptoms of schizophrenia, but they are not characteristic of catatonic schizophrenia.
**Option B:** Disorganized thinking and speech are features of disorganized schizophrenia, not catatonic schizophrenia.
**Option C:** Affective flattening is a feature of schizophrenia, but it is not a defining characteristic of catatonic schizophrenia.

**Clinical Pearl / High-Yield Fact**
The catatonic triad (immobility, waxy flexibility, and negativism) is a classic clinical feature of catatonic schizophrenia. This triad can be remembered using the mnemonic "ICAN" (Immobililty, Cannot be moved, Always resists).

**Correct Answer:** C.