What do the [..] mean in 'ps' and how do you create a process like it?

Square brackets are used for processes that do not have an associated command line (mostly kernel threads and some system services).

If I recall correctly, you might be able to achieve the same effect for your process by setting argv[0] to the empty string.

Yes, they are kernel threads, created by kernel subsystems. They are created using kthread_create() or kernel_thread() functions in kernel.

Your example doesn't even show the [...], so I'm not 100% sure what you're talking about. However it IS possible to modify the argv arguments of any program (in Linux). The arguments are reflected in the output of ps.