"DEAD FROM NEW YORK"
There were plenty of new TV shows presented in this episode, but mostly it was centered on an alt-Toobworld version of 'Saturday Night Live' called 'Saturday Night Tonight'. The murder investigation revolved around that week's SNT episode which was to be hosted by fading action star Danny Valentine with musical guest Carly Rae Jepsen (who played herself.) The crime was actually solved during the live broadcast of SNT and the murderer was brought down on set during a sketch which was spoofing the team of Detective Kate Beckett and author Richard Castle.
'Saturday Night Tonight' was created by Sid Ross in 1980 and had popular recurring sketch characters like Dr. Finger and Fluffy the Space Puppy. But it also had duds like the Mexican Wrestlers in the "Luche Libre Brunch Buffet" sketches from a few years back. (That probably was the same season that had the worst cast in the show's history*.)
The murder victim could be seen as Lorne Michaels, the head writer as Tina Fey, and one of the show's performers, a loose cannon of a comic, could have been based on Tracey Morgan.
But it was through Danny Valentine we got the mentions of the other TV shows in "Castle World":
- 'Hot Suspect'
- 'Family Practice'
and a series of rental car commercials.
(Based on those first two shows listed, I'm leaning toward Valentine being "inspired" by William Shatner, of 'Star Trek' and 'TJ Hooker' fame.)
The rental car commercials? I think it could be - should be! - for Gannon Car Rentals, best known in 'Lost', but also seen in:
Both 'Glee' and 'nip/tuck', like 'Lost', took place in Earth Prime-Time, unlike 'Castle'. ('Heroes' began in the main Toobworld, but Hiro created a divergent timeline which the show then followed, leaving the original iterations of the characters behind.)
But if Richard Castle and his daughter Alexis could be seen flying to London on an Oceanic Airways jet, then why couldn't Gannon Car Rentals be found in that dimension as well?
* I would not be surprised if all the people seen in the show's framed cast photos were crew members on 'Castle', getting in front of the camera for once. In a way....