1] 'Doctor Who'
This goes without saying. The format of 'Doctor Who' can accommodate any genre or guest star. A running gag could be that the Doctor tries to convince him that he knew the actual Lando Calrissian.
2] 'How I Met Your Mother'
An encounter between Billy Dee Williams and Barney Stinson would be legen - wait for it......*
3] 'The New Normal'
Could even the racist Nana Jane be able to withstand the smooth elan of Billy Dee Williams? I bet he could even talk her into going out with him!
4] 'The Glades'
People have appeared as themselves on police procedurals in the past - Kid Rock in an episode of 'CSI: NY' and Frank Gorshin on the original 'CSI', for example. But I think of all the procedurals, 'The Glades' would be the most fun because there could be a reunion between Billy Dee Williams and Kiele Sanchez, whose character of Nikki worked with him in the TV series 'Expose' in an episode of 'Lost'.
It seems like everybody in Hollywood has inner demons. But this time it could be that Billy Dee Williams needs the help of the Winchester brothers to fight them.
6] 'Franklin & Bash'
Who else is he going to call if he needs top legal representation in 'L.A.'? Well, okay, there are plenty of better options in Toobworld, but none quite as current or nearly as much fun!