Direct output to pipe and stdout

tee always writes to its standard output. If you want to send the data to a command in addition to the terminal where the standard output is already going, just use process substitution with that command. (Note that in spite of starting with >, process substitution does not redirect standard output, the tee command sees it as a parameter.)

fortune | tee >(pbcopy)

Your assumption:

fortune | tee >(?stdout?) | pbcopy

won't work because the fortune output will be written to standard out twice, so you will double the output to pbcopy.

In OSX (and other systems support /dev/std{out,err,in}), you can check it:

$ echo 1 | tee /dev/stdout | sed 's/1/2/'
2
2

output 2 twice instead of 1 and 2. tee outputs twice to stdout, and tee process's stdout is redirected to sed by the pipe, so all these outputs run through sed and you see double 2 here.

You must use other file descriptors, example standard error through /dev/stderr:

$ echo 1 | tee /dev/stderr | sed 's/1/2/'
1
2

or use tty to get the connected pseudo terminal:

$ echo 1 | tee "$(tty)" | sed 's/1/2/'
1
2

---

With zsh and multios option set, you don't need tee at all:

$ echo 1 >/dev/stderr | sed 's/1/2/'
1
2