MLP has made many mistakes in the past, but one they haven't noticed is that Minuette, Dr. Whooves, a pony named Romana, and a pony named Raggedy Doctor have the exact same cutie mark!!! If you look their cutie marks are both hourglasses which means that they control time and space. The cutie marks are supposed too be "unique to each and every pony, showing their special talent". There isn't supposed to be two of one cutie mark because they are supposed to be unique. The only difference I can see is that Dr. Whooves is a little darker than the other two.. If you know why this is, please tell me.
Minuette's cutie mark: http://mlp.wikia.com/wiki/Minuette
Dr. Whoove's cutie mark: http://mlp.wikia.com/wiki/Dr._Hooves
Raggedy Doctor's Cutie Mark: Found in List of ponies
Romana's Cutie Mark: Found in list of ponies
Another one I noticed. Lyra shares the same cutie mark as another currently unnmamed pony in "At The Gala" song. She appears right before Pinky Pie starts her part in the line. She has her mane puffed up, but if her mane was down she would look like cloudkicker. She has a harp exactly like Lyra's. Some other ponies with this cutie mark include:Ballad, Bee Bop
Another example from the Gala is during Raritys part, look at the gentlestallions that bow down. Some of them have the same cutie marks as well.
There are many more examples but one last one I want to point out to you is between Night Knight and a filly. both have a golden bow and arrow and are exactly the same (mostly) other than their age and mane (somewhat).
One other thing is that a lot of ponies have the same cutie mark and look alike (For example Derpy Hooves and Orange Box). Could this mean that MLP just takes ponies and changes the color fill to create more backround ponies? If so, why are the artists so lazy? Why don't they just ask for fanmade ponies, which would mean that they would get 1,000's of new ponies!
If you want to get a good example of color fill look at S01E11 Unnamed pegasus mare #3 and #2. Real good example.
I always knew thatthe MLP artisits made mistakes, but doing my research, it looks like they don't make mistakes here and there, it proves that they can be sloppy and lazy at times when they're in a time crunch.