Me: "My grandpa killed 100 nazis."
My friend: "Well, my grandpa killed Hitler."
The humor comes from the escalation of boasting. The first person makes a claim about their grandpa killing 100 nazis. The friend then one-ups them by saying their grandpa killed Hitler, the leader of the Nazis. It's funny because it's an absurd and unexpected jump in magnitude.
Comrade Communist
I raped Hitler in the ass while he begged for more. It appears it was not rape.
Anonymous
^ You're pathetic. Hope you grow out of your deluded fantasies soon
anonymous
bro took that personally
Anonymous
Hitler killed himself.... Is his grandpa Hitler??!?