1990 Anti-Drug special involved 4 networks and had lots of characters from different studios[0]
The Smurfs: Papa Smurf, Brainy Smurf, Hefty Smurf, and Clumsy Smurf
ALF: The Animated Series: ALF
Garfield and Friends: Garfield
Alvin and the Chipmunks: Alvin, Simon, and Theodore
The New Adventures of Winnie the Pooh: Winnie the Pooh, and Tigger
Muppet Babies: Baby Kermit, Baby Miss Piggy, and Baby Gonzo
The Real Ghostbusters: Slimer
Looney Tunes: Bugs Bunny, and Daffy Duck (Wile E. Coyote is mentioned but not seen; but his time machine is used by Bugs Bunny)
Teenage Mutant Ninja Turtles: Michelangelo (although he appears in the special, he is not shown on the poster and VHS cover)
DuckTales: Huey, Dewey, and Louie