In "The Demon Seed," Master Fung, Dojo, Kimiko, and Clay get turned into plants. While Raimundo and Omi are tending to them, Omi grabs some kind of apple from Clay's belt area and eats it, causing the horrified cowboy to protest, "Be careful what you go pluckin' there, partner!"
In "Treasure of the Blind Swordsman", the Blind Seer guarding it has a tendency to mishear things.
Blind Seer: (captured) Hold on! Where are you taking me? I have to use the bathroom!
Wuya: (To Jack) What about the treasure chest?
Blind Seer: What? That's disgusting!! (Beat) ...you talking to me?
Dudebot in "The Deep Freeze" basically commits suicide.
This exchange in The New Order:
Jack: Well, I've got something that you don't!
Chase: *smirking* Very small hands?
Jack: *annoyed* No.
Kimiko's "Fire!" Invocation can look a little questionable if you don't notice that she's wearing tights under her somewhat- Qipao-styled Xiaolin robe. Given that they are slightly lighter than she is, you might miss them.
In The Return of Master Monk Guan Raimundo calls Guan "Guano Man". The word "guano" basically means feces. Also, at the beginning of the episode, the Blind Swordsman summons an army of bats who relieve themselves on the monks and Dojo.