LOL! My son had a geography teacher who was a retired Marine. Probably the hardest class he ever had. They learned where every small country was in the world. He was glad to just pass the class!
This History teacher of mine was an Army Sargeant. Hell, some days he'd show up in his fatigues and scuffed combat boots.
He might have been crazy, but he was probably one of the coolest teachers I had back then. Every Friday he'd organize softball games in the spring. School basically ended after lunch as the rest of the high school class teachers also either participated or watched. Friday afternoons were cool.