Jack Nicholson -- Do I Look Like I'm Joking ... in This Courtside Selfie

Jack Nicholson upped the ante on duck-lip selfies by shooting his own ... of course he did it from $2500 COURTSIDE Lakers seats! Take that 25-year-old chicks.

76-year-old Jack struck the tired-ass pose with a cute blonde fan last night at Staples Center.

This was probably the closest he came to smiling last night since the Kobe Bryant-less Lakers got crushed by the Indiana Pacers 104-92.

Our best guess on Jack's thoughts during the game ... "This town team needs an enema!"