This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Poker Night 2
If Claptrap ties with Brock and Ash:
Claptrap: A tie?! That's like kissing your sister!
Ash: ...My sister's dead.
Brock: Mine too...
Sam: (sadly) I had a sister once... She was erased in a temporal anomaly...
Brock tries to remind GLaDOS of Cave Johnson, stating that Rusty told him that he used to hang out with the original Team Venture. GLaDOS can find no trace of him in her files, stating someone or something redacted all traces of Cave...then she begins to wonder why she feels sad.