No one expects a Marvel blockbuster like "Shang-Chi and the Legend of the Ten Rings" to be realistic, but just how much liberty does it take in the name of a good action sequence?

Katy and Shang-Chi are portrayed by actors Awkwafina and Simi Liu. (Disney)

A San Francisco bus driver's Twitter thread dissecting a fight scene that takes place on a moving city bus has gone viral and received the attention of the film's star, Simi Liu.

Mc "Mack" Allen told The San Francisco Chronicle he only started driving for the city's Muni service this month, but says he knows the system like the back of his hand, having been on every single line over the past 20 years. He watched the film for the first time after it premiered on Disney+ last week.

Driver Mc "Mack" Allen says he would've stopped the bus immediately if a fight like the one in "Shang-Chi" broke out. (Disney)

"I enjoyed the scene tremendously," he said. "I thought it was incredibly fun."

Allen's thread starts by pointing out that the scene starts with the bus already off of the 1 California line route indicated on it.

The bus is part of a fictitious transit system, but he uses the authentic Muni system as a reference point.

He also cuts right to the chase and points out that the moment the fight between Shang-Chi and Razor Fist's crew began he would've hit the brakes and opened the door.

He is quite sure, however, that someone would start filming or livestreaming the fight as Zach Cherry's character Klev does in the film.

Allen notes that the air hose for the braking system was cut during the fight and admonishes the driver for wearing headphones on the job.

"That's terrible. He definitely could be charged with an avoidable incident by SFT."

At this point, his training tells him to simply pull the parking/emergency brake handle, which the driver does not do.

He then explains that if the braking system had actually lost pressure, an alarm would've sounded and an automatic spring-activated brake would've activated and brought the bus to a stop anyway.

The driver also isn't wearing his seatbelt when the bus has a collision and his head slams into the steering wheel, knocking him out.

"Workmans Comp not going to cover this."

Allen chronicles how the bus takes an unrealistic route that would've required over 40 minutes to cover, but is heartened to see it smash through a row of share scooters.

"Every bus operator cheers when the scooters get mashed to shreds."

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He does credit Shang-Chi's friend Katy's knowledge when she takes the wheel.

"I'm impressed that she knew how to operate the door lever. When the doors are open, an interlock activates that prevents the bus from moving. This would also have been an option to try for an out of control bus."

Simi Lu responded "This is f**king amazing" to the thread, which has received over 40,000 likes so far along with recognition from San Francisco Mayor London Breed.

"Muni operators know Muni," Breed wrote.

The ultimate takeaway Allen hopes readers will get is that if something like this happens to you, just remember to pull that emergency brake handle.

As Fox News Autos previously reported, "Shang-Chi" also makes a major NASCAR reference mistake.