The joke:
Natasha extends her hand toward Leno and says, "There are three ladies in my hand." She then points to her palm and says, 'She's blonde, she's a brunette, and she's a redhead. Now I want you to pick up the blonde and put it by the side of your face."
Leno picks up the imaginary, tiny blonde out of Natasha's hand and places it against his cheek.
Natasha says, "Does that feel like the first time you made love?"
Leno says "No," so Natasha says, "OK, put her back! Put her back! Now pick up the brunette and put her against your face." (He does.) "Does that feel like the first time you did it?"
Leno said, "Uh, no."
"OK, put her back too. Ooooh, now pick up the redhead. She's a redhead. She's hot." (He puts the redhead against his face.) "That do it for you?"
A confused Leno says, "No."
"Not like the first time you had sex? Put her back."
"OK," Leno said as he put the redhead back into Natasha's hand.
"Now pick them all up," Natasha said.
Leno picked up all three and held them in his hand like dice.
"Now shakes them all up."
Leno shakes the women (looking like he's making a jerk-off motion).
"Now does that feel like the first time you..." Natasha asked.
Leno — realizing what she made him do — smiles awkwardly and says, "Oh, OK."