In 2015 Tweet released Grandmother Fish, a full-color, full-sized book about evolution aimed at preschoolers.

[2] Jonathan Tweet and Mark Rein-Hagen founded Lion Rampant in 1987 while they were attending St. Olaf College.

[5]: 232  His article "Egyptian Magic for Call of Cthulhu" appeared in Different Worlds #47 (Fall 1987), the magazine's final issue.

[5]: 234  Tweet wrote Festival of the Damned (1991), an adventure published by Atlas Games for Ars Magica.

[4] Lisa Stevens recommended to Wizards of the Coast to have Tweet work freelance to revise the Talislanta rules for Wizards to publish, and also write the first new adventure for their version of the game; Tweet also wrote a revised version of the Talislanta Guidebook (1992), and the adventure The Scent of the Beast (1992).

[5]: 277  Tweet wrote the adventure Apocalypse (1993) for the Role Aids line by Mayfair Games.

[8][9] 13th Age a d20 System RPG, designed by Heinsoo and Tweet was published by Pelgrane Press on August 3, 2013.

An atheist since grade school,[17] Tweet has devoted much of his personal website to his views on religion,[18][19] in particular on the historical Jesus.