This is for all of you who are bringing up that this is out of character for Gus. Nobody has mentioned the thing that actually does make it in character for him. PTSD. For those of you that know the show well, you'll remember that Gus had a partner when he first tried to get into the meth business. He tried to appeal to the cartel. He liked the guy very much ...
I believe it's because Walt and Jessie are the cause of the situation. Walt showed obvious displeasure in having Gale to work with rather than Jessie. He was bored with the guy and didn't vibe with him. I'd even go so far as to say he missed Jesse. The entire show displays a constant male role model relationship between Walt and Jessie. For walt, who had, ...
The episode is One Minute, and from Gale:
Despite Walt respecting and enjoying working with Gale, he was forced to fire him in order to prevent Jesse from filing a lawsuit against his brother-in-law Hank.
Well, it's all CGI.
They used CG dots to create a fly. They tried for real flies, but they had to replace these with CG flies.
They researched about fly's movements, variations in speed and directions etc to make it easier to shot like a real fly.
From this interview with Mat Beck,
fxg: The fly that seems to terrorize Walt and ...
That is just a music video of a narcocorrido song explaining that Heisenberg now has a reputation in Mexico and to show how the cartel feels about Heisenberg. If you look closely, the Heisenberg shown isn't even Walter White, but a younger person. The cartel don't know him, their only reference is the drawing.