It’s a crossover between Animaniacs and Tiny Toon Adventures!
“Lookit The Fuzzy Heads” is a short that aired as part of the 64th episode of Animaniacs. Written by Peter Hastings, it first aired on May 20th, 1994.
In the episode, Dr. Scratchansniff has the Warner Brothers (and the Warner Sister) in another session, but this time with a special guest, Elymra Duff!
The character of Elymra was one of the most well-known from Tiny Toon Adventures.