Closely related to Boob-Based Gag, as this may happen by Rule of Funny as well as Rule of Sexy. If the animation is exaggerated or silly, it may be accentuated by Stock Sound Effects to make it seems like a character's bouncing boobs are made of rubber or propelled by springs.

Also known as Gainax Bounce or the Gainax Bounce Effect. The term was coined by fans some time before 1993 and makes reference to the anime production of Studio Gainax, many of whose earlier releases made use of this particular variety of Fanservice. According to a Usenet post from 1993, one particular busty young woman from the Gainax anime Otaku no Video inspired a tongue-in-cheek unit of measurement for Gainaxing: one full bounce is apparently equal to one "Misty May".

Busty Bouncing