That’s an honest-to-goodness sweet potato.
Start the reactor, Quaid.
Quaid! Reactor! Now!
That’s not a sweet potato—that’s silly putty in disguise!
Sweet pooptato. 
There’s nothing wrong with it!
Did you start these from vines or plant whole small potatoes? Vines tend to make more and better-shaped sweet potatoes. Whole small ones usually just grow bigger and sometimes misshapen.
