I just enjoyed the recent "Off Topic" posts here, because, well... I'm me. But I do want to say that I think (and I may be biased) that INFJ is likely one of the most incorrectly typed types. Surely, there are millions of them, and of course they would flock here like the geriatric to Florida, buuuuut many of them are actually other types. Which is fine. And I don't even think intentional.
I think it's less "I want to be extra special" and more "I trusted the results of that one test I took". This is how it was with me, and probably the 5 other friends I had that tested as INFJ at the time (only one is clearly legit). For awhile, I theorized that it was because I was super unhealthy and in Shadow Function Land, but it's likely more simple than that. I always tested very low J. Then, after I learned the system and introspected more, I started consistently testing as INFP. Throw in a couple-o-withdrawn e-types and an Sp variant somewhere, and you got yoself a withdrawn extrovert.
There was, however, a time that I defended my INFJ typing like a rabid beast unaware of its own ailment, but it wasn't to be extra special. It was just pure stubbornness and intellectual arrogance, which is synonymous with foolishness.
Most likely to mistype as INFJ: INFP, ISFP, ISFJ, withdrawn ENFP, and maybe even some super confused INTx.
There are still plenty of the real deals.