The way that the punchline of the joke is delivered.
The punchlines are too long.
Nark Nark
Just spell it like the way it sounds!
Teutonic Plates. I'm sorry I'll find my own way out
Zzzzzzzzz, wait, I fell asleep at the punchline.
Ten. (Shame this one doesn't work too well for reddit - the funniest part of this joke is the third punchline enjoying people struggle to understand what the hell you're talking about.)
An explosive punchline
Two large planes