**Core Concept**
Intussusception is a serious medical condition where a part of the intestine folds into the adjacent part, causing obstruction and potentially leading to ischemia and necrosis. It is a pediatric emergency that requires prompt diagnosis and treatment. The classification of intussusception into different types is based on the location and extent of the invagination.

**Why the Correct Answer is Right**
The least common type of intussusception is the **Ileocolic intussusception**. This type occurs when the ileum invaginates into the colon, which is less frequent than the more common colocolic or ileocecal intussusceptions. Ileocolic intussusception is often associated with a lead point, such as a tumor or a Meckel's diverticulum, which can cause the intussusception to occur.

**Why Each Wrong Option is Incorrect**
* **Option A:** Colocolic intussusception is the most common type, accounting for approximately 50% of cases. This type occurs when a portion of the colon invaginates into another portion of the colon.
* **Option B:** Ileocecal intussusception is the second most common type, accounting for approximately 40% of cases. This type occurs when the ileum invaginates into the cecum.
* **Option C:** This option is not a recognized classification of intussusception.

**Clinical Pearl / High-Yield Fact**
In case of suspected intussusception, a pediatrician or surgeon should perform a careful physical examination and imaging studies to confirm the diagnosis. A rectal examination may reveal a sausage-shaped mass in the rectum. A high index of suspicion is necessary to diagnose intussusception, as the symptoms can be non-specific.

**Correct Answer: C.**