- Dawson Casting: Most egregious with Gwendoline Christie, who's portraying a 17-year-old when in her early 30s (an alien in costume, granted, but she also doubles in her human disguise so it shows there); Jefferson Hall (Varg) is in his 20s and his character is only a little older, so averted there. Scott Haran was 20 when his character (16-year-old Tom) first appeared, and Percelle Ascott is roughly the same age - not as bad, but still present.
- Real Life Writes the Plot: The entire series exists because it was devised as a temporary replacement for The Sarah Jane Adventures due to production of its fifth season being interrupted due to its star, Elisabeth Sladen, undergoing treatment for cancer. When Sladen died, there was no consideration given to continuing SJA without her, so Wizards vs. Aliens continued for a while longer, even making use of an unproduced SJA script (see below).
- Recycled Script: "The Thirteenth Floor" was originally a SJA story, but one which never began production.
Trivia / Wizards vs. Aliens