The best single example to use to demonstrate what the posters are talking about is the bit about riding into Jerusalem on a donkey. This is lifted directly from Zechariah (I don't have access to the exact passage at the moment, but can look it up later). In it, the prophet states that the messiah will be riding "an ass, and a colt, the foal of an ass". Most of the Gospel riders correctly interpreted this to mean a single, young, male donkey, the repetition simply being a poetic device.
Matthew, however, reads the original prophecy literally and invents rodeo Jesus where he is supposedly riding both animals (although I doubt at the same time). Seeing this type of discrepency highlights how the Gospel writers deliberately included prophecy into their accounts, even though it might not have matched reality very well (being written decades after the original events).