Anything you can dream, jankier

"committing it from the Crystallizer to the second skill check itself" - I don't think this step works. You can't commit an event to its own skill test when you're playing it from your hand. Double, Double lets you play it again "as if it were in your hand" and Crystallizer would let you commit it "as if it were in your hand".

I think we need a FAQ clarification for this interaction, because the reason you normally cannot commit the event to the event test itself is that you no longer have it in hand after you have played it, but if you resolve the effect of Double double first and then the one of the Crystallizer you should be fine, you don't phisically move the card (just as you don't move Luke to trigger his ability), so it remains attached to the Crystallizer and when it would be discarded it becomes attached again

I actually lean more that this interaction works as Gandalph says. If you read the FAQ in Jac FIne's starter set instructions it talks about resolving Crystal Pendulum and Scrying Mirror. Both of which are activated by "After a skill test at your location begins" to which the dev answer was you choose the order they are activated.

In this case you would add it to the Crystalizer and then Play it from your hand as you get to choose the order these are resolved since they are both activated by "After you play an event". Since it is first added to the Crystalizer I see no reason why it would not be eligible to be added as a skill card for it's replay.

Jank of the highest order. Nice!

As to your "as if it were in your hand." If I have two copies of Sneak By in my hand what's to stop me using one for the other's skill check? Is that in the rules? How I think about this interaction is basically the one event card is now in two places at once. It basically makes a second copy and they interact together as if you have two copies of that event card in your hand.

I don't think this works. Either you crystallize first or double first. Either way, when playing a card it leaves it's current zone. For example, if you play a card from hand, it is not in your hand during the resolution of the card (you can't commit it to itself). So in this case, you can crystallize it after playing just fine, but if you then trigger Double, Double, it becomes unattached and starts resolving and therefore can't be committed anymore. If you Double Double first, the whole event gets resolved before the Crystallizer trigger, at which point you can basically trigger it again, to attach the card twice, which doesn't do anything. There is just no notion of virtual card copies being attached to something, I think. There's never two cards. The second jank, playing an event, crystallizing it, committing it, and then getting it back to hand at the end of the round should work, in my opinion.

The order Double, Double -> Crystallizer doesn't even produce two Crystallizer triggers. If you trigger Double, Double on playing the event, the event is not discarded anymore, so the replacement effect from Crystallizer doesn't work. There is just nothing to replace.