Don’t know if this is any help, but it first appeared, alongside "Don’t You Think It’s Time" on the Original Sountrack CD for "Grace Of My Heart" (the Allison Anders film), released in 1996 but (C)’ed 1995 and credited to J Mascis. The booklet includes all song lyrics (yes, including TARATS & DYTIT- they look funny as acronyms, don’t they?), and a list of all musicians involved in the soundtrack / movie (curiously: no "J Mascis" on that list…), and though people like Flea, Chad Smith & Victoria Williams are among them, I couldn’t find any trace of possible J sidekicks for his tracks. The two songs, coupled w/ "The Pickle Song" then appeared as a bonus-cd / seperate 12" (UK) with the 1997 "Hand It Over" Album, this time credited to "Dinosaur Jr".
My guess is that J played all the instruments, but I also think there are guest vocalists, maybe Matt Dillon (like on "Hot Burrito #2"), since he stars in the film?