Some of the Shen Gong Wu hiding places don't make much sense. Take the Eye of Dashi, for example (hanging from a tree branch), or the Changing Chopsticks (Hanging out of the nostrils of an Easter Island head). Are we supposed to believe those Wu remained where they were, unnoticed and undisturbed, for 1500 years? Perhaps the worst offender is the Mikado Arm, which was on top of a skyscraper in mid-construction (What, did someone just carry it up there on a whim?)
While Jack Spicer of Xiaolin Showdown is considered an Ineffectual Sympathetic Villain, you'll notice that he's surprisingly fast and flexible, and can accomplish things like air somersaults even without the Mantis Flip Coin. Well, in one episode, it's revealed that Jack's mother sent him to figure skating lessons, which is why his body is trained to accomplish all the previous athletic feats. In connection with that, Jack is good at challenges that involve snow and/or ice, most prominently seen in Ring of the Nine Dragons where he was snowboarding quite impressively even before he cheated; this is most likely because the lessons took place in snowy or icy areas where Jack would have learnt the other sports as well.
Why is it that when Omi used the Ring of the Nine Dragons, even three clones resulted in them being immensely stupid (to the extent that one couldn't even get past level one of a video game) but when Jack uses it (the second time, for about eight clones) they can still perform normal activities and even comprehend rules and orders? Well, despite acting like an idiot in general Jack still isa genius, and so he has a larger IQ to distribute, resulting in each clone getting an average IQ instead of incredibly low ones like Omi's.
Why did Master Dashi seem so unsurprised to see Omi in "Days Past"? Because he already knew Omi from the events of "Time After Time!"
Master Monk Guan's nicknaming Raimundo "Bobo." Rai is from Brazil, where the official language is Portuguese. In Portuguese, "bobo" means "silly".
The Fountain of Hui, the Shen Gong Wu which provides limitless knowledge, is quite possibly named after the show's creator, Christy Hui, who is the person who has the most knowledge of the show's universe.
Why does Omi get jealous whenever his friends (eg Jermaine, Ping Pong) receive attention from the other monks? Its because they're his friends. Obviously he likes the person in question, so when the others start recognizing them, Omi is afraid that he'll be replaced. He then tries to prove he's better so that he won't be left behind, but because he does not get people, he ends up making everything worse before he lets go of his jealousy and admits to his mistakes.
How is it that, no matter how many times a Monster of the Week steals the entirety of the Vault, the Monks still have Shen-Gon-Wu for the showdown? Because they are Genre Savvy to hide Shen Gon Wu all over the temple.
Why are so many Shen-Gon-Wu similar in powers? Because they are Xiaolin Monks, plural. Dashi had a team just like the current monks, and if they had to go up against a foe weak against lightning, it would be best to have multiple types of lightning wu to increase the odds of victory.
In hindsight, the fact that evil can never truly be defeated should have been obvious. Why? Because Dashi, who at one point had both Shen Gong Wu needed to have the knowledge to permanently destroy evil, was a good guy. If it were possible to destroy evil and he had the means to do so, he would have done it. Since he didn't, then of course that means that it can't be done.