While this has nothing to do with Looney Tunes per se (sort of like the Johnny Bravo/Scooby Doo cartoon in one of my previous entries) it does feature two classic vocal effects from the great Mel Blanc.
"Super Mario Bros. Z" is an epic Youtube series created by a fellow named Mark Haynes, also known as "Alvin Earthworm". A couple years in the making and still ongoing, it is an all-out tribute to classic video games, with a plot modeled after the ridiculously long-winded and twisting plots of the anime series "Dragon Ball Z". If that doesn't sound like your cup of tea, you'll be pleasantly surprised...this thing is truly a work of art. Animated mostly in Flash and using graphics from old video games, the story chronicles a clash between the worlds of "Super Mario Bros." and "Sonic the Hedgehog". Sonic has a fight with an evil mechanical clone of himself over control of the "chaos emeralds", a bunch of gems from the Sonic games that, when combined, give their holder ultimate power. Sonic casts them into the Mushroom World of Mario to keep them out of the mechanical monster's reach, leading to a meeting of the Sonic and Mario "universes". It goes on seemingly forever, but it's entertaining as all get-out!
Anyway, the latest installment features a clever use of Mel Blanc's Yosemite Sam mutterings and Daffy Duck screams. See if you can catch them, and then check out the rest of the series, that is, if you have a lot of time on your hands!