@coolboymew @Moon You can't switch Assembly languages on the same hardware architecture as each architecture has its own instruction set. I assume you are talking about switching from Assembly to C.
From what I heard, Mario's Face was programmed in C++ while everything else was programmed in C and Assembly. It was also programmed by the only foreigner on the team, Giles Goddard. Maybe you can contact him on Twitter for clarification.
@coolboymew @Moon I assumed that they at least made some tech demos before they even started on SM64 and judging by leaked source code on some SNES and GameBoy games, some were at least partially programmed in C.
I've never heard about C code written by primarily Assembly programmers looking weird. I've heard of C programmers when using Java putting everything into a singleton object. It's probably similar to that.
Even if they were previously assembly programmers, I'm pretty sure their first programming language was probably a dialect of BASIC which is similar enough to C and probably wrote level and sprite editors in languages like C and Pascal.
@coolboymew @Moon Also, I expect SM64's source code to be a mess anyway because despite the C programming language being the primary language for the N64's API. It's different from traditional C code. In most C programs, the first function to be executed is main(). Apparently, the N64 uses a function called boot() when whatever game/software is being executed. There's a bunch of other stuff as well. The N64 was difficult to develop for compared to the PC and PlayStation, but not as difficult compared to the Sega Saturn.