Buck Henry, co-creator of Get Smart (1965) and writer of The Graduate (1967), used his clout as a judge to set up a screening at Filmex, the Los Angeles Film Festival, which was held at the Plitt Theaters in Century City in 1975. It was the first X-rated film allowed at Filmex, and the screening became legendary for the extraordinarily high ratio of walk-outs.
When filming wrapped on her 43rd birthday, Marion Eaton immediately began celebrating by lighting a joint. Suddenly, she remembered that they'd forgotten to shoot the important "Mr. Maple Tree" scene, so she alerted director Curt McDowell, who set up the camera and shot it in a single take.
An official DVD release was first announced in 2004, but it took more than a decade to happen. Synapse Films ultimately secured the rights and planned to issue it in 2010, but they were unaware that the existing film elements were in such poor condition. After years of restoration work, they were prepared to release it when 15 seconds of lost footage unexpectedly surfaced. Synapse paid for it at their own expense and then had to reauthor their master - which pushed back the release until December 2015, at the zero hour of the film's 40th anniversary.
The original negatives disappeared and only five 16mm prints of the film were struck. One print was seized by Canadian authorities and three had been edited in an ineffectual attempt to make the film more marketable. The badly damaged but uncut fifth print was primarily utilized for the transfer of the 40th anniversary Blu-Ray release by Synapse Films.
Coinciding with the film's release, The Roxie in San Francisco was rebranded as an arthouse theater. Director Curt McDowell was so broke that he took a janitor's position, and the movie regularly screened on Friday nights at 8 pm (it was decided that the film was too long to run at midnight). McDowell retained his job for many years and eventually married Robert Evans, one of the owners (although gay marriage was not legally recognized in that era). The theater continued to screen Thundercrack! and host retrospectives of McDowell's other films long after his death.