Let's say you watched a war-related movie, wherein the bomb was dropping down a city. And then, you storytell it to your interested friend.
Oh man, the movie was so intense! The aircraft dropped the bomb too fast!/ too fastly!
I think I've heard or read the usage of too fast similar to my example, and this is ungrammatical(I think) that even natives say that.
So is this an exception to the grammar rules now?