FlCl

[seeyouspacecowboy]

In one of the episodes (won't be hard to find because there is only like six) Naota's dad dresses up as Lupin the Third. He actually references it but I forgot exactly what he says. I know its a pretty obvious one but I wanted to post this regardless. I've been watching this show for a long time ( I think since it aired on AS) but I just realized it last year ( so I guess it's not that obvious huh?) I thought it was pretty interesting. 

[Chappi_The_Rabbit]

There's also the scene in the same episode (Brittle Bullet) when he hops out of his clothes to get to Haruko only for her to knock him out with a boxing glove attached to a spring between her legs, which is a parody of the opening of Lupin the 3rd with Lupin getting knocked out by Fujiko's boxing glove spring.

[boborudnik]

In Brittle Bullet as well, there's a reference to the "green one", the jacket color of Lupin III in "Castle of Caligstro"