I get it quite a bit with my two - some people know they are the "Turner and Hooch" dog, but most don't. I've even gotten into the habit of calling them French Mastiffs (which I hate saying) because when I tell people they are a Dogue de Bordeaux, they just look at me like I just grew a second head.
As puppies, people have called mine Golden Retrievers, Pugs, Bloodhounds, Shar-Peis, Boxers..etc.
What I thought was really funny was I had Fhalyn and Bub at the dog park last night. Bub was in the car (it wasn't very hot, the only reason he got to go - with all the windows down). I took the baby in and she played for a few minutes with some guys playing Frisbee. There weren't really any dogs that wanted to play with her, so I put her in the car and let Bub out to walk him around on leash for a few minutes outside the park. As the guys were leaving, one asked how much bigger Bub was gonna get - he had confused him for Fhalyn!! I mean I know they are the same color, but he's a good 5 inches taller and at least 85lbs heavier (not mention he has manly parts and she was wearing a pink collar while his is brown). Sometimes I can't believe how unobservant people are!!
What I also think is funny is when people don't even know what kind of dog they have - there was a couple with a EM about a year old at the dog park who were telling people he was a BM. I wasn't going to argue with him, but I would have bet $500 he was an EM! They'd had him since he was 6 wks old (so obviously not from a reputable breeder) and they were griping because he wasn't bigger (another pet peeve of mine). He was a good sized boy - I'm guessing at least 29in and prob. 160ish - in good lean condition.