A woman is pushing what appears to be a crash test dummy in a wheelchair down a hospital corridor.  A pair of elderly gentlemen are walking past them heading in the other direction.
It's unusual to see a crash test dummy in a hospital
Why is that crash test dummy being pushed around in a wheelchair?
I wish I had those knees.
scene: a hospital ward description: A woman is pushing what appears to be a crash test dummy in a wheelchair down a hospital corridor. A pair of elderly gentlemen are walking past them heading in the other direction. uncanny: It's unusual to see a crash test dummy in a hospital entities: Crash_test_dummy, Wheelchair. caption: I wish I had those knees.
A joke about old folks and body envy --- sometimes, people will see other people with physical characteristics they want and say/think "I wish I had those legs/arms/abs/etc.". But here, the old people are envious of a crash test dummy's knees, so the request comes across as one for a prosthetic knee replacement rather than something aesthetic.