Finally unlocked Wolf.
I decided to just go through the SSE until I found him. So now we have about 7 levels left with secrets.
Wolf is much cooler than I had expected. I was pretty pissed that the last character to unlock was a 2nd clone of a character I don't really like. But he's so badass.
But it did get me thinking. Some characters play really well, but are pretty unknown. Others are famous, but suck. Weird situation...