The Way of the Warrior (2) - S4-E2
Character mistake: During the Defiant's flight to save the Cardassian officials, Worf says something to the effect of, "I've never been aboard a Federation ship equipped with a cloak before". However, he was aboard the Enterprise during the Pegasus incident, where The Ship was temporarily equipped with a cloaking device.
The Way of the Warrior (2) - S4-E2
Revealing mistake: During the fight in Ops, the laws of physics takes a slight dive. While Worf is fighting the Klingons, he hits them with his Bat'leth or his mek'leth, and a second later they react to the hit.
Answer: He changed his name after the third season because people were having difficulty pronouncing his last name."Alexander Siddig" is the name he typically goes by as his full birth name, "Siddig El Tahir El Fadil El Siddig Abderahman Mohammed Ahmed Abdel Karim El Mahdi", is far too verbose and complex for screen credits.
MoonFaery ★