Yep, pizza (soda and/or beer as well) and Mortal Kombat.
It's a 'tradition' for me, my cousin and one of our friend. It started in the late 90's with Mortal Kombat Trilogy. We'd order pizza and play Mortal Kombat on whichever console we happened to have at the time (either we played MKs on my cousin's console when we went to his place, or my consoles when they came to my place, etc). We did that with MK Trilogy (N64 and PS1), MK4 [Gold] (on the Dreamcast), Deadly Alliance (PS2 mostly), Deception (PS2), Armageddon (PS2), vs DC Universe (on my cousin's 360 two or three times), and last but not least our favorite of all time the rebooted 2011 Mortal Kombat (it really is the best MK for me anyway, my cousin still prefers Ultimate MK 3 though).
Sure, ordering pizza with my cousin or with our friends to play games at their (or my) place happened other times and didn't only involve Mortal Kombat, but those occurrences were less common. With Mortal Kombat, however, it was Every. Single. Time. Which is why I easily associate pizza with the MK franchise.