Here's why:
* Subject: The subject of the sentence is "he".
* Verb: The verb is "talks".
* Agreement: The subject "he" is singular, and the verb "talks" is the singular form of the verb "to talk."
Therefore, the sentence is grammatically correct and does demonstrate subject-verb agreement.
The sentence "When he gets excited he talks his head off" is a good example of a simple sentence with a clear subject-verb relationship.