Canonical Jay Facts Masterlist

Born on August 16 [Detective Comics #790] (thanks anon)
Named after his grandfather [RHatO Rebirth #23] (thanks @darkmercury)
His adoptive mother’s full maiden name was Catherine Elizabeth Johnson [A Death in the Family, RHatO #0]
Was 4′6″ and weighed 87 pounds when he became Robin [Who’s Who: Update ‘87 #5] (thanks @jasontoddenthusiastt)
Died on April 27th at age 15 [his death certificate]
Was 5′4″ when he died [The New Teen Titans #55] (thanks @prodigworl)
Claims he started drinking liquor at age 8 🥴 [RHatO Rebirth] (thanks @darkmercury)
Had an erector set when he was young [Detective Comics #479] (thanks @goodoldfashionedengineer)
Chilidogs were his favorite (Bruce won’t touch ‘em) [Gotham Knights #43] as was Alfred’s pot roast [Detective Comics #569] (thanks @jasontoddx)
Isn’t a fan of Alfred’s waffles (and neither is Tim) [RHatO #8]
“He loved cars and girls and getting into fights... neapolitan ice cream and the color green...” [Detective Comics #790]
Was a fan of Poison Idea, Eric Peters, and Rebel Kind [Batman: Second Chances] (thanks anon)
An absolutely adorable Superman fanboy ♥ [Action Comics #594]
Thought there was nothing worse than mimes, heh [Batman: Second Chances]
Played baseball [Detective Comics #574, Gotham Knights #45]
Probably knows how to play the electric guitar since there's one in his old bedroom [RHatO #17] (thanks @baeson-todd)
Attended Thomas Wayne Middle School for 3 months [Batman and Robin #25] (thanks anon)
Though he dropped out of school in the fifth grade he was able to master computer science concepts at age 12-13 [Batman: Second Chances]
At some point before his death he had a 94.8 GPA (and the most adorable shit-eating smirk ever, hehehe) [Batman Annual #12]
Learned to read lips at age 12 [Red Hood: The Lost Days]
He’s a polyglot; he knows at least German, Russian [Red Hood: The Lost Days], Arabic [A Death in the Family] (thanks @cerusee), and Portuguese (though he says he's rusty at it) [Batman Eternal #18] (thanks @skalidra)
Could steal cars as well as tires [Nightwing: Year One #6]
Before becoming Robin he had a best friend named Max Dawkins [Truth & Justice #10] (thanks @robiinjason)
Didn’t have any friends after becoming Robin ;__; [Batman Annual #12]
Was penpals with Kid Devil [Blue Devil #19, Teen Titans Vol 3 #42] (thanks anon)
There are people in Gotham who have his autograph from when he was Robin 🥲 [Detective Comics #570] (thanks @yvtro)
He remembered intricate details about the Batmobile’s security system [Red Hood: The Lost Days] and was able to bypass this system in order to install a bomb he made [Red Hood: The Lost Days] at this age (thanks @marileibis)
Knows how to bypass Wayne Manor’s security [Batman Eternal #10]
Knew about whatever the fuck he’s talking about here [Secret Origins #5] (via @nightcrawler-fan: “The topics he was discussing were about identifying the kinds of tissue found in the brain, unless I’m mistaken.”)
He is immune to brainwashing [Red Hood/Arsenal] (thanks @feyrewymack)
Has either a photographic memory or a power called adoptive muscle memory [RHatO #25 or #26] (thanks @storiesaremylife)
Reads Jane Austen novels [Batman and Robin #23] and lots more! (thanks @thecruellestmonth)
He’s a houseplant daddy! [Wayne Family Adventures #31]
He knows how to play the piano [Gotham Knights] (thanks @wrdn-tabris)