Celebrity impersonations abound; not only is Drak, Jr. voiced in the style of Don Adams (with frequent references to Get Smart), but Vampira is given Eva Gabor's Hungarian accent, while Toad is voiced in the style of Peter Lorre (to say nothing of a passing resemblance).
While Drak, Jr. is frequently referred to as Dracula's nephew, he's technically (according to the first episode) his great-nephew, as Dracula states he is the boy's "great-uncle".
Howler's powerful breath is generally considered to be a reference to the Big Bad Wolf of fairy tale fame, though it's never actually stated.