The Danza: An early episode featured TV talk show host/supermodel/superhero Vendela, voiced by Norweigan-Swedish model and actress Vendela Kirsebom. Like the other examples of Celebrity Star, this doubles a highly(?) fictionalized version of As Himself.
In Spain, Johnny is Private in The Penguins of Madagascar, which is interesting because his English (and German) voice actor, Oliver Feld, is Kowalski in said series.
Keep Circulating the Tapes: Only the first season ever got an official DVD release along with a few other episodes pieced on some of Cartoon Neworks holiday DVDs, though the entire series is available on iTunes, and the first season has become available on Netflix.
Talking to Himself: The Danish dub played this straight in the Scooby-Doo Cross Over. Lars Thiesgaard, who regularly voices Scooby and Johnny, voiced both in that episode.