“He’s so big!” I exclaimed.

“He’s the same size he’s always been,” my curmudgeonly neighbor retorted.

I eyed the dog. No, he was definitely bigger than when I last saw him, almost a year ago. “No, I think he’s bigger. It’s been almost a year.”

“He’s five years old.” And he stared at me as though this meant something.

“Yes?” I asked with arched eyebrows.

“Don’t you know that mammals only grow during their first year of life? Then they stop growing.”

I looked at him as though he were testing me. Was this a joke? It didn’t seem to be. I thought for a moment.

“Aren’t humans mammals? Don’t they continue growing past their first year?” He stared at me. “I would beg to differ with your theory.”

“Whatever,” he retorted, and walked away.