Plural of "uh-oh" and "oh-no"
Solution 1:
I asked my meme-minded son to check his texts. In this little electronic corpus, he found seven instances of "oh noes!!!" with no hyphen, no apostrophe, and too many exclamation points.
An official source is Merriam-Webster's New Words and Slang, which includes oh noes.
Solution 2:
I don't see any reason the plural should use an apostrophe in the "uh-oh" case. Indeed, if we check google ngrams for "uh-oh's" vs "uh-ohs", we see that there is no usage of "uh-oh's", but some (and increasing!) usage of "uh-ohs". Furthermore, use of "ohs" is far more common that of "oh's" (as seen here).
However, in the "oh-no" case, an apostrophe might be appropriate. We can see that "no's" is the most common plural of "no" here.
I'd also like to mention that, while "uh-oh" is far more common that "uh oh", it seems that "oh no" is actually the more common form of that interjection, as can be seen here, so the most proper plurals might be "uh-ohs" and "oh no's", respectively.
Solution 3:
A cursory googling suggests 73000 results for "oh-no's", 113000 for "oh-nos" and 2170000 for "oh-noes" — however, the latter has become a meme, skewing the numbers. The dictionary lists plurals for "no" of "noes" (first) and "nos" (second). I also find I'm getting annoyed by the massive overuse of apostrophes in the world, but that's not quite germane.
I'd suggest "oh-noes" or "oh-nos", or "oh-no"s if you're a radical.