Appearing as himself, the former astronaut and second man on the Moon provided the League of Themselves link between '30 Rock' and the following shows and TV movies:
'The Fall Guy'
'The Boy In The Plastic Bubble'
'Da Ali G Show'
'Space Ghost: Coast To Coast'
'Head Of The Class'
His appearance on 'The Simpsons' took place in the Tooniverse, of course, and there is no connection - unlike the 'Space Ghost: Coast To Coast' episode where he was getting beamed into the Tooniverse from back on Earth Prime-Time.
I'm such a geek......