Tanks For The Memories - S5-E15
Factual error: Tim accidentally fires an M2 .50 machine gun while on a tank. Ricochets are shown sparking all over other tanks while people dive for cover. A) Bullets don't spark when they ricochet, and B) the M2 had a blank firing adapter installed; it couldn't have been firing bullets.
The Secret of the Unicorn: Part 1 - S1-E3
Factual error: The man selling the Unicorn tells Tintin that he can have it for 25 dollars. Tintin is Belgian and this is in his home town; they should be using francs in that time period. (00:03:30)