The transformation from a guys casual facial expression to the one he puts on right before he goes for the pink cave.
A mixture of a fake smile and complete fear.
Fake smile because he promised he loved giving oral
complete fear for what he might find and/or smell
Between bros and dudes it is often refered to as PLF
Example #1: She was smokin hot braw, and I wanted her so bad so I just had to put my PLF on.
Dan the virgin: DUDE she gave me a blowjob, now I have to go down on her, but that place looks fucking scary.
Vinnie the experianced: Just get your Pussy licking face on and act like it is the best thing ever.