"The Ghost of the Bad Humour Man" it was called and it was in the 1st season of The Scooby-Doo Show ... but it's still a really good episode I agree with that!
That episode was broadcasted as an episode of Scooby Doo Where Are You the third season and is considered part of Where Are You and The Scooby Doo Show.
that third season clip intro was technically a misnomer. sure it aired that way...but the format is a little more high stakes than where are you was...so it's sds. they just never had a seperate name for it until after all stars.