The reason why Tiny Toon Adventures (1990) wasn't mention in the "Which is Steven's favorite show?" argument is because the show was airing on Nickelodeon at the time. While Freakazoid! (1995), Pinky and the Brain (1995), & Animaniacs (1993) aired on Kids WB.
The memo that Freakazoid shows Wakko is based on a real memo that Paul Rugg received from Steven Spielberg. In real life, the memo was regarding "Animaniacs" (1993), not "Freakazoid!".
The opening scene in which Freakazoid does favors for various people, is a takeoff on 'The Godfather.'
The names on Cosgrove's list of people waiting to see Freakazoid include "Deniro" and "Pacino," both of whom started in installments of 'The Godfather.' The names "Sinatra" and "Stallone" are also visible.
In line waiting to see Freakazoid are Joan Rivers, Rush Limbaugh, Bill Clinton, Lady Di, the Pope, Rooster Cogburn, Kramer from 'Seinfeld,' Jim Carrey as 'The Mask,' and Judge Lance Ito.