Today I came across this video, shot some 3 years ago by a junior, capturing Karunakaran sir in action. Watch the video below.
You'll have to tilt your head or screen to get correct view of the video.
Jobs like teaching can become boring after sometime when one has to teach same topic again and again (Add to this the possibilities of poor pay, non cooperation of students and other factors) and it becomes more of a routine. It is amazing to see that he still retains all his energy, enthusiasm and passion. Wishing him long life and all the best.