BFDI usually animates on 2s or 3s (12-15 frames per second). If you try to use a complex mouth asset with 24 different shapes, it will look too fluid and "Disney," which ruins the staccato, snappy humor of the show.
The genius of the BFDI mouth is its mathematical purity. Unlike the fluid, squash-and-stretch animation of Disney or the manic overbites of anime, the BFDI mouth operates on a rigid, binary system. bfdi mouth asset
In the early 2010s, internet bandwidth was slower, and animation needed to be efficient. The Huang brothers developed a "cutout animation" style. Instead of redrawing characters frame-by-frame, they used —reusable pieces of art. BFDI usually animates on 2s or 3s (12-15 frames per second)
Look closely at official BFDI assets. The edges of the mouth are not perfectly smooth vector curves; they often have a slight, almost imperceptible flatness on the top and bottom to simulate a stylized "bean" shape. Unlike the fluid, squash-and-stretch animation of Disney or
The asset's simplicity and accessibility have led to it being used far beyond its original context:
Simple vector shapes; often included shaded teeth and tongues.