Past tense and the phrase "who knows what"

The phrase "who knows what" and other variations of it refer to unknown things, for a lack of a better descriptor. When writing a story in the past tense, would this phrase change?

His pocket contained a key ring, spare coins, folded-up slips of paper, and who knows what else.

Compared to:

His pocket contained a key ring, spare coins, folded-up slips of paper, who knew what else.

Is using the present tense considered inconsistent? Is one preferable to the other?

Solution 1:

who knows what and who knows what else are English idiomatic expressions. (I know them from British English, but the citations below suggest they are also common in American English.)

who knows what
One or more things described with no detail.
Our junk drawer has old remotes, instruction manuals, and who knows what else in it.
You're supposed to be doing your homework, but instead you're slacking off and doing who knows what!

Because it's an idiomatic expression, it's generally treated as a single entity (I think the technical term is 'noun phrase'). Hence, it is not appropriate to change knows to knew because it is not serving independently as a verb, but merely as a component of the phrase.

As the definition above indicates, it is used to refer to one or more things (or even actions – see the second example sentence above "doing who knows what!) that are either not worth mentioning individually and/or are unknown.

Here are some websites that use the expression in their titles:

What I'm Thinking and Who Knows What Else
Jewelry design and who knows what else…
Dances, Romances, Who Knows What Else

and a sentence from a website:

Google may dabble in hardware, driverless cars, and who knows what else, but it makes the bulk of its money on advertising.

and here it's used as a website tag: who knows what else

In conclusion, knows is not being used as a verb, and hence does not change tense. It is not being used to refer to "who knew what" at the time that "[h]is pocket" was being examined, and therefore the past tense would be inappropriate.