Missing a end bracket:

menu channel,nicklist,query {
  .D4n's Mimicer
  ..Mimic Person:/mimic $$?="Person to mimic:"
  ..End Mimic:/mimic.off
}

This can be shortend

on *:text:*:%channel: {
  if ($group(#mimic).status == on) {
    if ($nick == %mimic.person) {
      if ($nick :ACTION: %:ACTION:person) {
        msg $chan $1-
      }
    }
  }
}

to

on *:text:*:%channel: {
  if ($group(#mimic).status == on) && ($nick == %mimic.person) && ($nick :ACTION: %:ACTION:person) {
    msg $chan $1-
  }
}