Well, this Animaniacs short is probably one of the funniest outtake injokes ever. It is a nearly word-for-word re-creation of one of Orson Welles' famous commercial outtakes, where he is supposed to read ad copy for frozen peas, fish fingers, and (under protest) beef burgers, but ends up arguing semantics with the director, wailing and gnashing about how he'd NEVER direct actors that way, and is just plain cranky all the way through. (Someone's gone and made a YouTube "re-enactment of Welles' tantrum; few cusses in there and they mislabel it as the Paul Masson "mwahaaaaaa, the French" outtake, so just turn off your monitor or close your eyes and listen. Actually, the guy performing as Welles there does an amazing job, so watch him at least. He also plays one of the directors, too.)
I remember when the Animaniacs episode first aired, too, and me and my entire cadre of cartoon-watching friends (4:00 pm everyday, Dickinson Hall lounge) had a damn hard time understanding it. This was before we could get ahold of such outtakes, those bootleg bits of ephemera notorious among The Industry (if you say "Cradle them" in an Arnold Schwarzenegger voice and I'm in the right mood, that will crack my shit up.) These clips have since enjoyed broader exposure thanks to The Internet but at the time, we had no idea what the hell it was about. And if we Sophisticated College Cartoon-Watching Types couldn't get it, surely the actual children in the viewing audience wouldn't either. I believe "Yes, Always!" still ranks as the most cryptic Animaniacs short ever.
But once you've heard Orson's infamous commercial voiceover tantrum and then watch the cartoon, it's damn amazing. The dialogue, the timing, the inflections, everything except for a few pottymouth expressions. Maurice LaMarche, an incredibly talented voice actor and impressionist, used Welles' voice for The Brain, so it's only natural that they thought it'd be hilarious to take such a dig with what, at the time, was a rather well-kept injoke.
Of course, nowadays I'm glad they did it, but back in 1994, I was all bummed out cause we got that instead of a Goodfeathers short ("If you give me one more iota of aggravation, I'm gonna peck open your brainbox and let all the air out.") Or, if we were really good and ate all our vegetables, maybe we coulda instead seen the brilliant parody which fused Apocalypse Now with Jerry Lewis' infamous never-released The Day The Clown Cried (Wakko doing tai chi on the top of a WB studio golf cart while Frank Welker of all people sings "This is the middle... the middle of our story..." is one of the funniest things I've ever seen animated.) The Interbutt had already explained to me the Jerry Lewis bit, so it was all good.
Oh, and adding to the plethora of injokes in the Pinky & The Brain cartoon is the crew that the Brain throws out at the beginning of the piece. Yes, they're caricatures of the Animaniacs producer, writer, voice director, etc. Probably their own voices, too.
LaMarche was also responsible for Welles' voice in both Ed Wood and in the episode of The Critic where Welles shills for "Rosebud Peas ... full of good, green peaness..."