When one part of an argument doesn't properly overlap with another portion of the argument, an undistributed (or incorrectly distributed) middle term can result. Note the following examples:
Example: All Bigfoots eat chickens. Mr. Spagnolo's favorite food is chicken wings. Mr. Spagnolo is a Bigfoot.
(The premise doesn't clarify that Bigfoots aren't the only beings that eat chickens; therefore, the conclusion that follows the logic above will be incorrect.)
Example: Mr. Spagnolo has big ears. All dogs have big ears. Mr. Spagnolo is a dog.
(The premise doesn't specify that creatures other than dogs can have big ears; therefore, the conclusion clearly is incorrect.)
Yes, this is first two examples are "no brainers" and are obviously incorrect, but note the complexity of these examples.