I was thinking about the old "Boo Boo Baba Dee Dee" commercial.....
Boo Boo Baba Dee Dee ☆Great Quality☆ - YouTube
I had thought the singing voices were just voices..... But now it hits me that maybe those were supposed to be Cartoon Network characters singing (and we don't see who is singing). And maybe I am wrong, maybe it was just the voice actors doing the same voices but not intentionally their characters. But I started thinking about how one of the voices sounds like Johnny Bravo, and then another sounds like Space Ghost.... then I kept figuring out that so many matched other characters.
I hear the voices of Brak, Chicken, Johnny Bravo, Dee Dee, Dexter, Space Ghost, and The Red Guy. There is a voice or two that I can't quite identify (sounds like it's supposed to be maybe Daffy Duck but I also feel that's not right). With the exception of the Space Ghost characters, those are all Cartoon Network original characters (and even then, the Space Ghost characters were on a CN-original series at the time, and I think those voices are best remembered for them as opposed to the original Space Ghost and Dino Boy voices).
I was watching The Nostalgia Critic's recent video about Cartoon Network bumpers (this one wasn't in there), and it hit me that the Looney Tunes rarely appeared in bumpers with original animation (but there was the one where the characters answer questions from viewers, such as "what would Sylvester do if he ever caught Tweety?"). It was often Hanna Barberra, Cartoon Cartoon, and MGM characters. Makes sense to leave out Looney Tunes in early promos, but after 1997, they should have been fully allowed to include the Looney Tunes.
Seems there were also a few promos to focus on obscure Hanna Barberra characters..... around that time, there was one where security would not let Yogi Bear in because he forgot his ID (and they can't figure out who he is). I wonder if that commercial would have been as funny if it was a fairly obscure HB character.