Jillian Holtzmann took the initiative to develop Proton Sidearms. She finished almost all of them except the Proton Grenade Launcher by the time the Ghostbusters met Mayor Bradley. The launcher was introduced with the other Proton Sidearms. Holtzmann invited Erin Gilbert to pick any one. Erin picked up the Proton Grenade Launcher. Holtzmann freaked out and told her that one wasn't ready but when it was, she could have it. She handed her a Swiss Army Knife then one of the Proton Grenades. Erin strapped the launcher to her right leg in a leg holster then headed to Times Square to find the other Ghostbusters. Erin used the Proton Grenade Launcher to repel Gertrude Aldridge and the Electrocuted Ghost at the same time as they rushed her. They were blown away. Erin was surprised by its power.
- It was developed along with the Proton Blaster and they share some design traits.
- Both weapons were called "Proton Side Arms" during production.
- A early design of the "Proton Side Arm" were used in designing the Mattel toy, the Sidearm Proton Blaster.
- The Proton Grenade Launcher features a side-folding gunstock.
- Erin tried to quote the famous line, "Say hello to my little friend" from "Scarface" when she used the grenade launcher.
- In the "Full Version of the Times Square Fight" featurette, the Proton Grenade Launcher was originally going to overload after it was used then Holtzmann threw it towards the 1966 Rambler and the ghosts near it, where it exploded. Holtzmann admits she never tested it.
- Holder, Nancy (July 2016). Ghostbusters, p. 237. Tom Doherty Associates, LLC, New York NY USA, ISBN 076538843X. Narrator says: "Holtzmann had also created two kinds of grenades--'air filters' and 'test tubes'-- plus a proton grenade launcher for Erin and a 'drop-down' gun for herself."
- Jillian Holtzmann (2016). Ghostbusters (2016 Movie) Extended Edition; Chapter 14 (2016) (Blu-Ray ts. 1:44:40-1:44:42). Sony Pictures. Jillian Holtzmann says: "Guys, you all have your sidearms."
- Jillian Holtzmann (2016). Ghostbusters (2016 Movie) Extended Edition; Chapter 11 (2016) (Blu-Ray ts. 1:15:14-1:15:18). Sony Pictures. Jillian Holtzmann says: "No! I'm sorry, not that gun. That one's not ready. It's yours when it is."