The Blue Lotus: Part 1 - S1-E8
Revealing mistake: Just after the Chinese man gets shot, he starts sweating. Right as he finishes saying "We need help", part of the sweat sliding down his face just slides onto his tooth and continues down onto his face. (00:02:45)
The Blue Lotus: Part 1 - S1-E8
Revealing mistake: Tintin leaves Mitsuhirato's office with a Chinese guy watching him. Look at his food on the table. Only one side of the bowl has food in it. The other side is empty and magically manages to hold still. (00:05:45)
The Blue Lotus: Part 1 - S1-E8
Revealing mistake: After the car that tried to shoot at Tintin drives off, we can see stuff that was shot at the wall falling to the ground, unnaturally slowly. (00:06:15)
The Blue Lotus: Part 1 - S1-E8
Revealing mistake: In the wide shot of Mitsuhirato's car driving through the woods, no car is visible in shot, just the car's lights. (00:15:55)
The Blue Lotus: Part 1 - S1-E8
Revealing mistake: When Tintin says "Take this" to Mitsuhirato, his skin is green/yellow. (00:19:25)
Answer: According to Wikipedia, he is described as being a youth anywhere from 14 - 19 years old. There is no specific age.
raywest ★