I just told a story in the comments section that I decided I wanted to make into an open post.
My husband is Army, and I've had minimal exposure to the other branches of service. But I attended job training in Germany with people stationed all over Europe, so I got to meet some nice Air Force and Navy spouses. One Navy wife was telling a story about her husband, and I cheerfully said, "Your husband's a lieutenant? So's mine!"
She was so polite and nice that she didn't even point out that an Army lieutenant is as low as it gets on the totem pole and a Navy lieutenant is just a wee bit cooler. It wasn't until I got home that my husband pointed out what a bonehead I am.
So what are your bonehead stories when it came to learning to identify rank?