The Cat Ear-Shaped Headphones are a mysterious object that was given to Hidomi Hibajiri by her father. It is unknown when they were made or what they are fully capable of. Whenever Hidomi wears them and feels extreme emotions, they activate a security protocol to block her N.O. channel. However, this has been bypassed several times, such as when a red horn and robots came out of her forehead, she created a cybernetic arm, and N.O.-infused metal floated around her. They can also change color depending on Hidomi's emotional state. They were created by Medical Mechanica and can drill into the wearer's skull so that they can't be removed. Because of this, Hidomi decides to take a stand by continuing to wear them when she realizes why Haruko Haruhara wants her to remove them. At the end of FLCL Progressive, Hidomi removes them of her own volition and Canti destroys them.
The Cat Ear-Shaped Headphones appear as predominantly black headphones with cat-like ears on top and light blue highlights. The blue appears to be from LED lights, highlighting the ears' housing with two rings on the sides and the cat ears with two indented triangles that give the illusion of depth. They also have a jagged Medical Mechanica logo etched into the end of the adjustable portion above the housing.
Some sort of engine part is hidden in the housing, only visible when the headphones are activated. It has fan-like pieces seen spinning in the gap for the LED lights and makes a whirring noise that often quickly amplifies in response to radical circumstances, as if being overloaded. When activated to suppress N.O. power, the lights change color from blue to red.
The headphones have the ability to detect N.O. and can suppress it. The lights turn from blue to red when N.O. is detected and something within the headphones begins spinning, creating a sound similar to an engine. This also occurs when trying to remove the headphones, wherein they drill into the wearer's skull to prevent the removal. This also allows them to control the wearer's thoughts directly. The headphones are able to modify the wearer's thoughts and personality to be nothing short of complete positivity, as most other emotions, such as stress or anger, trigger N.O. activity. The only way to deactivate this ability is the destruction of the Medical Mechanica factory that allows it to function, returning the headphones to their neutral blue state. Outside of this, they are also able play music when Hidomi plugs her phone into them, indicating a Bluetooth-like feature.
The headphones were created by Medical Mechanica at an unknown time for the purpose of detecting and suppressing an individual's N.O.. Hidomi's father obtained them at some point in the past, either with or without MM's permission, and gave them to Hidomi as a gift before leaving town. Since that time, she has used them to symbolically "put the world on pause," presumably wearing them nonstop before she is introduced with them on in Progressive, as she's even seen sleeping with them on.
- Despite always being shown with the LED lights on, it's never shown or questioned if the headphones are rechargeable. They could possibly be powered by Hidomi’s own N.O.
- They are based on the Cat Ear Headphones made by Axent Wear.
- A piece of concept art shows Aiko with the headphones. It's unclear if she was ever planned to be their owner or obtain them from Hidomi.