Jason Porath:

If you’ve seen Big Hero Six, chances are that one of the things that stuck with you was Baymax’s “balalala” fist bump. You can see the exact moment in the YouTube clip above. Most people saw that and just laughed at the silliness of it.

Me, I set my watch.

Upon first seeing it, I guessed (correctly) that exact gag would be repeated 2-3 more times in the movie, depending on how well the test audiences had enjoyed it. They would be spaced out for maximum effect, at 20 minute intervals.  And that it would be seized upon by the marketing department, either in the trailers themselves, the TV ads, or a twitter campaign (it was, as you can tell by the above video). I even guessed that it was inserted fairly late in production (which, best I can tell from what my Disney friends have said, is also true). I would not be surprised if it was one of many such moments that were tested out.

But it feels so good! See also Ohrwurm, and animated movies are just the first to get it, it will be coming to all media soon.