Other mistake: In the voice cast list, the Groom's Father appears twice - with two different voice actors - and the Groom's Mother is not even listed.
Ben 10 vs. The Negative 10: Part 2 - S4-E9
Continuity mistake: As we could see in first season's final episode, "Secrets", Roosevelt's head on Mt. Rushmore was totally destroyed, and in most subsequent episodes - including this one's first part - there is a sizable hole in its place. But after Ben asks whether the plumbers' hologram technology can replicate 'big presidents', and the scene changes to the demolished presidents' heads, the crown of Roosevelt's head suddenly joins the others on the mountainside.
Plot hole: When the mutated sea gull attacks the Tennyson's' sailing boat, it brings down the sail. But then the piece from under which Ben and Gwen emerge suddenly has a convenient wooden lattice fixed to it, whereas in reality it should have none.
Continuity mistake: The priest who presides over the wedding gets a faceful of muck by the bride's parents. When he flees the scene, screaming, he is peachy-clean, but later, as the ceremony is happily concluded, he suddenly has muck stains on his head and robe.
Ben 10 vs. The Negative 10: Part 2 - S4-E9
Plot hole: Rojo (from first season's "The Alliance") makes her second appearance in the series in a suit of powered armor. However, in "The Alliance" she had been turned into a cyborg by Vilgax' drone and thus looked radically different than she does here. So how can Max say: "How did she get back her alien tech?" when her equipment and weaponry was totally different in their first encounter?
