Beta version of my first LoRA ever, so it might produce low-quality results sometimes, especially for full-body images and when used with other LoRAs.

Describing the expression in detail might yield better results:

his eyes wide open and his mouth open, tongue sticking out.

his tongue sticking out and a thin stream of saliva is visible from his mouth

He has a surprised expression

 His facial expression is one of intense pleasure

or you can use the lora with just the trigger words gooner face and gooning