Because old hobbits die hard. (Just a different Punchline)
Well an erection of course.
They only have an erection every 4 years
He got kilt.
Because people are dying to get in there.
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.)
Because old Hobbits die hard...
Bruce Willis. Because old hobbits die hard.