I’ve had a problem that’s seriously bugged me.
Whenever I try to model anything with mirroring and apply a subsurf modifier, I always get a little crease on the tail.
What’s going on? I get why it does it, but this never happens to anyone in tutorials. Is there any way to stop this from happening?
Hard to say exactly since you haven’t linked your file, but you probably have internal faces. Turn the subsurf off for a moment and check that there are no faces right in the middle.
Check to see if you have merge and clipping turned on, and also remember to put the subsurf AFTER the mirror in the stack.