At 01:53 of episode 4 of Kyoukai no Kanata: Mini Theater special, after Hiroomi said that Mitsuki was his only idol, this conversation happened (transcribed to the best of my ability):
Kuriyama: メガ盛｛も｝り 金平ごぼう、 ですか？
If my guesses are right, Kuriyama mistook MK5 (emu-kei-go) as abbreviation for Megamori (large serving) Kinpira1 Gobou2, which is a Japanese dish.
Image from http://cookpad.com/recipe/1743175
My question is about "MK5" in Kanbara's line. While the line can be generally understood as Mitsuki was getting pissed off at Hiroomi, I don't get what Kanbara is making a reference of by saying "MK5". Any idea?