Strip by: David Morgan-Mar
T-Rex: T-Rex presents The Periodic Table:
T-Rex: 43 TECHNETIUM
T-Rex: The first element for which all isotopes are radioactive. Half lives range from days to 4.2 million years, so there's almost none naturally occurring on Earth. The first sample was created unintentionally and then
T-Rex: SENT THROUGH THE MAIL!
T-Rex: I know! If only Marty had gone back to 1936, Doc Brown could have just mail ordered some technetium!
T-Rex: That would have been such a better movie.
T-Rex: Except Marty's GRANDMA would have kissed him on the lips.
The author writes:
 Technetium, Official discovery and later history. Italian physicist Emilio Segrè visited the Lawrence Berkeley National Laboratory in California in 1936. He wanted some of the discarded bits of the Berkeley cyclotron, which had been rendered radioactive by the particle bombardment produced by the device, so he could study them. Ernest Lawrence agreed and sent him a bit of irradiated molybdenum foil through the mail. Back in Italy, Segrè analysed the radioactive foil and found the first evidence of the element technetium.
You wouldn't get away with this nowadays. Australia Post, at least, specifically prohibits sending radioactive material through the post. (Australia Post also prohibits mailing live animals, with exceptions allowed for bees, leeches, silkworms, "other harmless insects", and international mailing of "parasites and destroyers of noxious insects... exchanged between officially recognised institutions of both countries".)