Yeah, "ramdon" was an invention of the person who did the localization in the subtitles. The actual dish is known as jjapaguri, which is similarly a combination of two sorts of instant noodles. In order to convey that it's a combination of instant noodles to western audiences, "ramdon" was invented because it was assumed that western audiences would be more familiar with ramen and udon than the actual instant noodle products that were being combined.
(Another bit that's also changed in the translation, they just say "sirloin" when the actual thing the mother asked for is hanwoo, which is basically high-end steak, sorta the Korean equivalent of wagyu or kobe beef. Sirloin kinda undersells the degree to which they're adding something only available to the very rich with cheap instant noodles, although the generic "steak = rich" thing does get across a lot of the same intent.)
Apparently the standard version of the dish combines 2 instant noodle packets from the Korean brand Nongshim, Chapagetti and Neoguri. So if you're trying to recreate it, those are what you'd want to seek out.
