Say all you want about the Angry Birds and Green Pig's rivalry, but this image of the Angry Birds and Green Pigs celebrating christmas together (Even having the King Pig dressing up as Santa Claus and happily giving out presents to the birds and pigs) is an unusual yet very wonderful sight to behold! ◊
The video for the second Christmas themed expansion. We could go over all the tropes as to why it's Heartwarming, but it's better if you see for yourself.
As strange as it may seem, this anti-bullying video of the Black Bird defending a little pig from Three Evil Mexican Pigs is a sweet sight to behold, even though the green pigs are naturally the enemies of the angry birds. 
At the end of the Angry Birds Trilogy Trailer, we see the CGI-Animated White, Blue, Yellow, and Red Birds laughing and having a great time while sitting on a couch, like any happy family would! Isn't that adorable or what?