Other mistake: Lois digs up Chloe's grave site to unearth her casket. It is obvious that the casket is not buried six feet deep. You would think, with all that is going on, that LuthorCorp would have at least buried the casket deeper to deter inquisitive eyes and maybe throw in a few scattered bones for good measure.
The Breach - S2-E21
Other mistake: As Archer walks into the sickbay, while the camera pans, you can see a bottle of Crystal Geyser water. I noticed the bottle right away but had to pause it to see the brand. (00:39:00 - 00:40:00)
Injustice For All (2) - S1-E19
Other mistake: Unless he escaped prison, it makes no sense for Copperhead to be in the police van with the other Secret Society members. You can see him sitting there across from Solomon Grundy and The Shade.
Other mistake: Two Tiffs can be seen for a few seconds when King Dedede and Escargoon drive in.
Other mistake: In this episode, Eric tries to destroy a mutant, apparently unaware that Rangers don't destroy mutants but freeze them. Yet in Quantum Quest and Clash for Control, he froze a mutant.