Process:

The very first sentence is easy, "Hi, I am Baymax, your personal health care companion." is repeated a lot of times throughout the movie, so it's easy to find. The it became harder, words like "you", "should", "friends","I" appears a lot of times, but often within a sentence and are very hard to isolate. Finally, negative words are rare. At first I wanted to use "I killed Tadashi", but then I found out Baymax had never said the word "kill", so I had to use "hurt" which was only used once in the movie and is blurry. I had to adjust the speed and duration of some words at the end to make the sounds clearer. 

The last part, the end video effect is actually a part of a video on youtube. I tried to build one myself but failed. So I just search on Youtube and find one that best fit.