The scene where Spock has Saavik pilot the Enterprise out of spacedock. Kirk is trying his level-best not to be scared out of his wits by the fact Spock is making her do it without any prior experience.
McCoy: Would you like a tranquilizer?
[Kirk quickly shakes his head]
When they share a turbolift, Saavik is utterly oblivious to Kirk's attempts at flirting. Followed by McCoy (who's been waiting for the lift) snapping, "Who's been holding up the damn elevator?"
Kirk, McCoy and Saavik are about to beam to Spacelab:
Spock: Jim... be careful.
Kirk and company are about to follow Carol and David's last transporter coordinates, which are inside the desolate rocky planet:
When Kirk is climbing down the levels with Spock on the way to the bridge, Kirk tells him, "That young man there. That's my son!" Spock replies in the most bored tone of voice, "Fascinating." For an unemotional being, Spock is certainly expressing his non-interest in a very emotional way!
One could also read plenty of sarcasm into Spock's reply, too. As if to say, "You sleep around so much, of course you'd eventually come upon a son."