The part is Window Round 3 x 3 x 2 (73878).
It was a new mold for 2021, and one of its first uses was as windows on Andrea's House (41449).
This piece can be used on buildings anywhere you'd like a curved window. It is easy to imagine how it could have been used on earlier sets, such as the "curved" windows on the Pet Shop:
This part introduces ...
I could only find minifigure head with same face expression but with freckles:
Minifigure, Head Dark Brown Eyebrows, Dark Orange Freckles, Open Mouth Crooked Smile Pattern (Jay) - Hollow Stud (3626cpb1872)
While I cannot yet confirm if this is the only piece with such face expression, it is not unheard of such modification (within LEGO community), where ...