Bravo 3 is a droid who is an employee of Dr. Namyzarc and Associates. Not much is known about Bravo 3, except the fact that they are the assistant and right-hand-man of Dr. Namyzarc. They help the doctor while he is recording or giving a presentation, such as bringing subjects in for questioning, running analysis' on items, or operating the camera. There are a few instances of Dr. Namyzarc talking off screen to Bravo 3, yet as of this point in time, we have never actually seen their physical appearance.
The first instance of Dr. Namyzarc mentioning Bravo 3 is in the video "This Will Be The End Of ASMR", however there is an instance before this where Dr. Namyzarc speaks to something off screen named "Beta 2". Beta 2 is actually just an old laptop, as stated by Dr. Namyzarc here, and it seems that Beta 2 was thrown away in later videos in favor of Bravo 3. Despite the fact that Dr. Namyzarc says that Beta 2 cannot speak, he talks to it as if it can, implying that he might be a bit of a crazy man.