I promise that Grandma has the best of intentions..

Grandma and Grandpa suddenly learn they have a Trans grandkid, and since this was something that wasn't talked about, they just knew nothing about. So they look for information to educate themselves. They use the internet a little bit, but then they ask their daughter (the mom to the trans kid.) Mind you, the Trans kid is NOT in the room when this happens, and that's why I think it is funny.

Grandpa: Well a pediatrician probably doesn't come across more then a few Transgenders in their Career.

Mother: Transgender people. 'Transgenders' is not a word.

Grandpa: I'm learning the language from you, dear..

Grandma: ( totally innocent look on her face ) Not Trannys?

Mother: ( oh god no! look on her face ) No!!!!!!

Grandma: ( face drops into sour lemon, immeadiately realizes she F'd up and panics so she repeats the mother ) No!!!!

awkward silence

Mother: That.. that's a really bad insult.