Ear Worm: "Pappara funi funi pappara hoe hoe, Pappara funi funi tamago!" Being set to an amalgamation of Beethoven'sSymphony no. 7, 4th Movement, Symphony no. 5, and Symphony no. 9 helps.
Germans Love David Hasselhoff: The two episodes animated did poorly in Japan, so no further episodes were made. However, this made it really cheap to license, and its bizarre humor struck a chord with American audiences (also, it was one of the earliest subs made available), which made it a beloved classic amongst them.
Harsher in Hindsight: Damaramu demonstrating his machine gun by blowing a space shuttle out of the sky would probably be seen in bad taste after the Columbia disaster.
Les Yay: In the manga, especially between Mink and Rufa. It's very one-sided on Rufa's part, though.