Other mistake: In first episode Wells apologizes for locking up Clarke's dad, then acts surprised when she tells him he got executed, when in episode 3 it's revealed they both assisted in the execution.
The 100 (2014)
1 mistake in show generally - chronological order
Starring: Eliza Taylor, Paige Turco, Marie Avgeropoulos, Thomas McDonell
Remember Me - S2-E9
Kane: Peace with the grounders is the only way we'll survive.
Abby: Oh, I don't think they know what 'peace' is.
Kane: The Commander does.
Abby: She's a child. They're being led by a child.
Kane: So are we.