Revealing mistake: We can see Ecliptor's zipper from behind - slightly revealing on Saban's part, considering Ecliptor is supposed to be an evil monster henchman of Astromena's.
The Powerpuff Girls Best Rainy Day Adventure Ever / Just Desserts - S2-E10
Revealing mistake: When the van drives upstairs, you can see that it wasn't destroyed.
Deathfist 5: Major Crimes Unit - S2-E15
Revealing mistake: There's a stunt featuring two-way too obvious body doubles for Kelly Hu and Gretchen Egolf rolling over a table; not only the stunt itself is rather underwhelming and blatant, but also the objects on the table disappear just so the two can perform it.
Revealing mistake: When Gamora is warning Silver Surfer to think about what he is saying, the gallery of characters behind her are the exact same on both mezzanines.