ふざけた顔

A yellow face with its head tilted, its tongue hanging out of a big grin, and wide eyes in a wild, cockeyed expression. Generally used to express silliness.

Commonly represents acting goofy, having fun, and partying and is usually used in a positive manner. May be used in reference to someone or something that is off-kilter.

Microsoft, and WhatsApp previously displayed a full-toothed grin instead of an open mouth with a protruding tongue, which appeared less silly and more menacing. Google's design used to show the mouth in a grimace, which also read as more disturbing than silly.