Just the guilt in his face when he realises this
I mean, it wasn't his fault. Like he said, he thought they were abandoned, and just wanted to look after them (and project onto them slightly), so he was just doing what he thought was the right thing, but all he probably did was keep them away from the rest of their species and family for a bit longer. He did nothing wrong here, but now he knows the truth, he's probably gonna feel really guilty, even though it wasn't his fault

Again, just accepting things happening
"Oh golly, I'm having spears pointed at me from an unknown species. Huh that's interesting"

Me trying to explain the plot of this episode to my family who don't watch the show because I have no one to talk to about this

Also I love how he has to explain that they're aliens, like that wasn't obvious from the everything about them

Ok I can't tell you how much I love this sequence. It's all just so smooth, it's really good
And it's so interesting learning about what happened
The fact that there is another egg somewhere out there though is concerning, because if Cobs has it, it's bad for the creatures inside because god knows what he will do with them, but if Fan happens to find it, and they catch him with it, they might think that he stole both of them on purpose, and if they think this is the case, it probably won't end well for Fan, Test Tube, or anyone else who tries to stick up for them.

Also it explains why they just straight away jumped to attacking Mephone when he did nothing to them(which I didn't even pick up on until my 20th time watching)