The Jitterbug is a nonlethal concussive device developed by Howard Stark.
The Jitterbug was a creation of Howard Stark made prior to 1942 and the death of Carole Lombard. During its creation, Stark remembered the measurements of flings that he had had and used them as codes toward the activation of different capabilities in the Jitterbug; Carole Lombard had the measurements 34-24-34, while Barbara Stanwyck measured at 33-23-33.
Peggy Carter and Edwin Jarvis suspected that they were going into a trap set by Whitney Frost as they made an attempt to rescue Dottie Underwood so Jarvis demonstrated the Jitterbug to Carter to show her that it could help them to avoid an ambush from her Maggia bodyguards. Jarvis had Carter, who teased that the invention looked like a biscuit oven, stand behind him as he typed the code 34-24-34; a concussive blast was emitted from the Jitterbug that destroyed the lawn furniture on Howard Stark's Estate.
Arriving at the Chadwick Ranch, Edwin Jarvis carried the Jitterbug with Peggy Carter covering him with her rifle; he set up the invention as Maggia men converged on the two. Jarvis patiently waited for the right moment to activate the device when he pushed the code 33-23-33; nothing happened. Jarvis and Carter quickly surrendered.
While in captivity, Jarvis wondered what he did wrong as he eventually freed himself. He realized that he had used the measurements of Barbara Stanwyck instead those of Carole Lombard. As Peggy Carter and Dottie Underwood asked what the difference was to how the Jitterbug would react, a massive explosion occurred. Jarvis explained that he activated the delayed reaction sequence in the Jitterbug; the three saw Maggia men unconscious before them as they escaped.
The Jitterbug can fire a nonlethal concussive wave in a blast radius of 170 degrees. In order for the design to be activated, the proper code needs to be inputted into the keypad. 34-24-34 is the code for instantaneous firing and 33-23-33 is the code for delayed detonation.