There are a few. The most popular being Jason, who led the Argonauts and was Medea's husband.
There is also:
Jacchus, the daemon who led the procession of the Eleusinian Mysteries.
Japetus, one of the Titan brothers imprisoned by Zeus in the pit of Tartarus.
and Jasion, an consort of the goddess Demeter.
Theoi.com is a good site for Greek mythology for you want more details
Jughead.. from Archie comic series.
Jerry from the Tom & Jerry cartoon is an animated character. Jane Jetson from The Jetsons is an animated character.
Jason, leader of the Argonauts in Greek legend
Jenny Willis Jefferson was a character on The Jeffersons. Her name begins with the letter J.
Hera is a mythological goddess. Mythological goddesses never reveal their ages.
No there is no Mario character that starts with a J
An attitude starting with J is jolly.
J.-Charles-J Luce de Lancival has written: 'Hector' -- subject(s): Accessible book, Drama, Hector (Legendary character), Helen of Troy (Greek mythology), Parodies, imitations, Plays
Considering that there is no "J" in the Greek Alphabet, my inclination would be to say "no".
J. J. Coulton has written: 'Greek architects at work' -- subject(s): Architecture, Greek Architecture, History 'The architectural development of the Greek stoa' -- subject(s): Antiquities, Stoas
Examples of nouns starting with J are:jackjackaljacketjackrabbitjadejaguarjailjalopyjamJamaicajamboreeJanuaryJapanjarjasminejasperjavelinjawjayjazzjealousyjeerjellyjellyfishjeopardyjetjeweljewelryjimsonweedjinglejittersjoggerjokejonquilJordanjournaljourneyjubileejudgejuggernautjugularJulyjumperJunejunglejuniperjunkJupiterjuryjustice
An activity starting with J is jumping rope.