And immediately after, when Buzz tries to defy reality by flying off the stairwell railing. After crashing to the floor, he glances over to where his arm popped off at the ball joint, and despairs...
Especially the way Newman slowly sings the lyrics towards the end.
And how the sudden uplift makes you hope that somehow, in spite of him being a toy, Buzz will pull it off. You maybe even think that he will for a moment.....
The song "Strange Things". Woody starts off playing with Andy and then suddenly Buzz is taking his place and Woody is staring around in shock at the way the room, and effectively his whole world, is changing so rapidly around him...
Bo Peep watching Andy sleep without either of his favorite toys ("Oh Woody. If only you could see how much Andy misses you").
What really hurts is the fact that Bo and Slinky were the only ones who believed that Woody was innocent (until the arm scene.)
When Woody admits to Buzz his fear of getting replaced:
Woody: Look, over in that house is a boy that thinks you are the greatest, and it's not because you're a space ranger, pal; it's because you are a toy. You are his toy.
Buzz: But why would Andy want me?
Woody: Why would Andy want you? Look at you! You're a Buzz Lightyear! Any other toy would give up its moving parts just to be you. You've got wings, you glow in the dark, you talk! You helmet does that, that, that woosh thing. You are a cool toy! (pause) As a matter of fact, you're too cool. I mean... I mean what chance does a toy like me have against a Buzz Lightyear Action Figure? All I can do is (pulls string) *voice box: there's a snake in my boots*. Why would Andy ever want to play with me, when he's got you? I should be the one strapped to that rocket.