A 68-year-old grandfather named Malcolm Myatt who suffered a stroke back in 2004 claims that it has taken away the ability to feel sad.

After spending 19 weeks in the hospital, it was found that the stroke had affected the part of Malcom's brain that controls emotions, leading him to be dubbed "Mr. Happy" by the British media.  But it's not all sunshine and rainbows, and Malcolm's wife also said he's lost the ability to judge what is and isn't appropriate to say in public.
"It's worst when we go to a funeral. He'll still be smiling and telling jokes while everyone else is completely somber," she said. "Most of the time people know him and understand, but we do try to keep him to one side just in case."
The American Stroke Association confirms that, because a stroke impacts the brain, a victim's personality can be affected. But Malcolm's case is unique since depression is the most common emotional change experienced after a stroke.

The Telegraph