Bug: Wheat, carrots, and potatoes sometimes won't grow on certain blocks. In the picture you can see two potato crops that haven't begun to grow surrounded by fully grown potatoes.
To Reproduce: Build a farm and let it go for a while. When all the crops should be fully grown, look for baby plants.
Edit: Melons and pumpkins also won't grow on certain blocks.
Note: If you cannot reproduce, I figure its probably some corrupted blocks that appeared during my switches of jar files. These blocks are from the original world which began around 1.2.5