There's also a brilliant sight gag she provides during the doll side-quest. In fact, this whole sequence during the Fidget doll quest is just a series of greatly delivered funny lines stacked on top of one another.
In the sheep-fetching quest when Dust just picks up the first sheep:
It's also even funnier when you consider how much of a jerk Gianni is to the heroes and how he abandons Corbin, the young boy who he first sent to do his laundry, out alone in the Ivydale Glen. Basically, our heroes are guiding karma to teach Gianni a lesson.
Glop, the senile old man in Mudpot, has his moments of funny dialogue when asking the heroes to get his "hittin' stick", find some trolk fingers and some rock-hound teeth.
Going to the room where Tim is hidden yields a pretty funny and playful Take That! at Braid and all its endless symbolism and hidden meanings:
Fidget: Well, that made absolutely no sense.
Dust: Every moment has a purpose, Fidget. You just have to dig deeper!
Or maybe she's complaining about how this was the hardest sidequest puzzle in the game. It's not marked on the map, you have to look closely enough at an inventory item to notice the mark on it, you have to remember where that corresponding mark is in a level with a lot of particle effects on-screen, and then you have to crouch there for about ten seconds without moving.
It could also be a playful Take That! against a very similar (read: exact same) puzzle from Castlevania II: Simon's Quest which is frequently referenced by those who critique the game, as the puzzle was so opaque, many didn't find out the solution until much later.
At one point in the game, Dust proposes that the only way to proceed is to cause massive avalanches on a mountain, which Fidget wholeheartedly agrees upon. This causes Ahrah to actually break his normal mystic wise tone to deliver his own shocked line.
Ahrah: Really? I have to be the voice of reason here?!
Later, Fidget has a prolonged bout of sneezing and poor(er) judgment, after which she complains that she's coming down with something. The first response?
Ahrah: Yes, Fidget. We figured that out on our own.
The "Friends" you can free when you unlock their cages can cause some WTF?-caused laughs. With the first cage you might stumble upon, you'd probably expect some sort of cel-shaded anthro like the rest of the characters in the game. Who do you get instead? Meat Boy As in, the 2D skinless archenemy of Dr. Fetus. That Meat Boy.
The outtakes, heard here. Highlights include Lady Tethys having trouble pronouncing her name, Dust saying "mudbloods" instead of moonbloods, and Michael Johnston (out of character) musing about putting a bath towel in the freezer followed by him speaking in tongues.