Yes. It's an ad that popped between parts of mlp:fim several times, and people complained about ads. But everytime the "GAK ad" was here, people were writting the looping music : "GAK GAK GAK".

I was in a Steam chat with 10 people, not even knowing what was going on in the "official" rooms, and we still chatted "GAK GAK GAK" everytime. At the end of the episode, one of us created a steam group named "GAK GAK GAK". It's very memetic.

You poor man, you weren't available for the live stream. :(