(at around 20 mins) There is a newspaper that contains a number of Muppets references, including an apparent Fozzie Bear review.
M-66 is the only anime production in which creator Shirow Masamune had direct involvement in.
In the last few minutes of the OAV, Sybil can be found wearing an Apple Seed shirt, clearly a reference to one of Shirow's other works.
The screen in Sybel's apartment towards the end has some text about the army and then the following (German) text: "Das...Quelle Institut für Warenprüfung Qualitäts-Anforderungen ganz entsprechen" This doesn't make much sense in German. Literally, it reads: "The...source institute for checking goods, quality requirements are fully equivalent to"