Alder and Dash are the main antagonists of Casper's Scare School both the film and TV show.
Alder and Dash first appeared in Casper's scare school movie where they introduce as the headmasters of Scare school the were tired of their job so they decided to take over the world of both monsters and humans first by getting rid of Kibosh. Their plans were stopped by the return of their "Ankle" (Aunt & Uncle), Belle and Murray.
In the Tv series they serve as the main villains from time to time and always try to scheme their evil plans but Casper always foils them.
They loved their Ankle who was banished because they were too nice.Their names are a pun on balderdash. Their appearance have two heads on one body and Alder is the head on the left and Dash is the one on the right,Although they sometimes never got along with each other and in the series they make ridciouslos plans that never pan out like they wanted to.They delight of the suffering of the students and being manipluative towards anyone to achive world domination but always fails due to Casper.
Dash is smarter and more conniving than Alder, who is slower on uptake, but has good ideas occasionally. However, in season 2, Alder seems to have more lines than Dash and more serious and smarter and there are tiny amount of schemes there.