"Dear Martian Friends, we regrettably discovered sentient pebbles while searching for Milky Way souvenirs. No postcards from them, please. They're a bit rocky. Sincerely, The Voyager Crew."
"Dear Earthlings, Neptune's nebulous hues are no match for Friday-shift fluorescent lighting. Do send us more oxygen. Love, The Submarine Crew."
"Dear Residents of Terra, we seem lost. Can someone send directions back to the launchpad? Kind regards, Apollo's Backpack."