The title is a double-entendre pun in Japanese. On the face of it, "Onna Deka Melon" means "Lady Detective Melon." However "deka" is also a slang way of saying "dekai" or "large," and, of course, melons are a slang term for breasts. So, an alternative reading of the title is "The Lady's Big Breasts."
The episode is mostly based on one of the Lupin manga stories, with a notable exception: in the manga, Melon was a man who would serve for a number of stories as Zenigata's unwanted partner/rival, and who had a preternatural skill at throwing handcuffs.
Also known as "Revenge of La Nerd."
This episode marks the second appearance of Ganimard's descendants, after the appearance of Ganimard III in the first series. No mention is made of this previous encounter, however.
The scene with the train tunnel is inspired by the chapter with the Tokyopop title "The Lupin who Loved Me".