Orphans vs. Vegans

Alright, listen up, you chucklehead. This "joke" is saying that just like vegans are known for constantly talking about their diet, making it hard to forget them, nice orphans are so forgettable that nobody remembers them. It's playing on stereotypes, which, based on your comedic sensibilities, is probably the only way you understand humor anyway. You are probably as forgettable as those orphans.