When yawning as part of the yawn emote, your face shrinks down (This was done to "fix" an issue when Walter yawns, but ended up looking weird for everybody else).
Furthermore, yawning for any other reason (i.e. Bearger yawning, Panflutes in pvp or eating a Mandrake) uses the unshrunk face and it is also missing the layer that the glasses for Wilson's Verdant skin are on.
Lastly, when doing the emote yawn, beards look like they go above Wilson's nose. Maybe this is just me not understanding the perspective properly though.
Yawn in a variety of different contexts.