Hollywood hunk Colin Farrell's "Late Show", is generally fun-and-games. But what came as a surprise was when Farrell brought spoke on The Ellen Show, about his son's rare disease, the Angelman Syndrome.

Genetics Home Reference, defines Angelman Syndrome as a "complex genetic disorder that primarily affects the nervous system".

The disease is associated with signs and symptoms of cerebral palsy, although there are a lot of differences between the two diseases. Angelman Syndrome affects only one in 20,000 people.

What is Angelman Syndrome?

"Children with Angelman Syndrome typically have a happy, excitable demeanor with frequent smiling, laughter, and hand-flapping movements. Hyperactivity and a short attention span are common. Most affected children also have difficulty sleeping and need less sleep than usual. Some affected individuals have unusually fair skin and light-colored hair," according to Genetics home reference.

But then, the affected individuals continue to have intellectual disability, severe speech impairment, and seizures throughout their lives.

Farrell's son is pretty high-functioning and is also a very happy boy. Farrell also admitted that he can't be too upset with his son's diagnosis, because he is always smiling and happy.