mansplain.sh

mansplain() {
  user=`echo $USER | tr "[:lower:]" "[:upper:]"`

  # ugh, macos vs linux
  if command -v gzcat
  then
    _cat() { gzcat $@; }
  else
    _cat() { zcat $@; }
  fi

  # set pager if not set
  if [ -z ${PAGER+x} ]; then PAGER=less; fi

  _cat --force `man -w $1` | sed -E -e "s/\.SH \"?NAME\"?/.SH \"WELL ACTUALLY, $user, LET ME EXPLAIN...\"/" | groff -man -Tutf8 | $PAGER
}

I don't know about other distros, but on Ubuntu manpages are zipped, so you need zcat instead of cat.

Fixed, added a lot of armor to make it cross platform.