A full body puppet is a costume-scale figure worn by a performer who is entirely inside it, rather than operating it from below or behind.
The best known example
is Big Bird, performed for nearly fifty years by Caroll SpinneyCaroll Spinney (1933–2019) performed Big Bird and Oscar th... with one arm raised above his head working the head and beak, the other inside a wing, and a small monitorThe monitor is the screen a puppeteer watches while performi... strapped to his chest showing what the camera saw.
What makes it hard
The performer cannot see out. Vision comes from a monitor, a mesh panel, or a gap in the costume that is never where you need it. Every movement has to be executed blind or by screen, including walking across a set without hitting anything.
Heat is the limiting factor
A sealed foam-and-fabric costume under studio lights is brutal. Working periods are short, cooling breaks are scheduled, and many builds include fans or ventilation channels as structural features rather than luxuries.
Building for it
Weight distribution matters more than total weight — a head carried on a harness at the shoulders is manageable where the same weight held out on one arm is not. Access for the performer, ventilation, sight provision and quick removal all need designing in from the start.
Proportion for the camera
Full body characters read as awkward when built to human proportion, because a human is underneath. Exaggerating the head and shortening the apparent legs is what makes the figure read as a character rather than a person in a suit.
Related forms
parade and giant puppets, mascot construction, and body puppets where the performer is visible and part of the design.
The hack: build the ventilation first. Everything else can be adjusted later; airflow cannot be added to a finished costume.