I went into pep boys for a filter kit for a 200c, looked up a 87 cutlass, ect... Only a th250 came up. After the guy arguing that I was wrong, it had to be a 250, I bought the kit, then brought it back with the trans pan that the gasket didn't line up to and had the stamping "METRIC 200" right in it. Looked it up for an 86, and I got what I needed.
Bought hoses for my cutlass at advance auto, girl asked "2 door or 4 door" I said "doesn't matter" She said smugly "well, it does". So i said "ok 2 door." She brings out the hoses and the top hose is about 8" long. So I tell her it's the wrong hose and tell her to look up the 4 door hose, she refused and told me "This must be the right one..." Well, I went back the next day and spoke to a guy I knew, he looked up a 4 door and got me what I needed.
I have so many more...