darkSpyro

I hit the last troll in the challenge the same time I hit a painting after I decided to do another challenge then the painting broke and I could hear Cali saying something on the heroic challenge select screen.

That happens to me all the time.
EDIT: In the first game, that is.

Silly Cali...

I've also successfully completed a quest after technically failed it. Kill the 2nd purple chompie (in which you also kill the last chompie) or 2nd painting while destroying the 40th enemy and you'll both start to see the failing animation while it rewards you. Very funny.

Never done the Purple Chompies in Giants, don't have a S2 of that character (Drobot I think... LC is pathetic, the regular is only just coming out, and I already have S1), but in SSA there are no purple chompies anywhere near the last green ones, so not sure how you'd pass/fail that one. But I THINK I've pass/failed a challenge before.

^ Depends on the way you go where the last ones are.

In that one, no, not really. There's a pretty well defined path to go, anything else is a lot of backtracking, and you'd run out of time. (Again, this is SSA, not SG).

Out of the first big room, cross to where you have to choose between a square room with 4 green chompies or another hall, which are the only exits to this area. Take the hall and immediately go downhill to the left (up on the screen). If you don't go downhill, after that is two green chompies and only purple ones after that, leading to a dead-end room. At the bottom of the hill, lakeside, is a handful of greens, then it's a dead end, so back up the hill to the 4 green chompies. This catwalk-like dock is blocked at the other end, so you can only descend into the room. From here, there's only one exit, an uphill hall which returns to overlook the last room. Once you enter this hall, there's no more purple chompies.

With all of those dead ends, and the time being so tight, that's the only path.