You can't push good tabletop (or PbP) game humor. Sometimes you just have to patiently sit and wait.
If anything, the Grue is patient. One learns these parentally-taught lessons ("Tasty humans come to grue who wait," and "An adventurer in the claw is worth two in the light" are some of my favorites) at an early age. And so he sits. And waits.
After some time (who knows how long - the Grue's watch does not have Indiglo, for obvious reasons), a darkness dims the horizon as the Grue joins what, at first, appears to be just another PbP game shortly before the holiday season (a lonely time for many a grue, working their dungeons all alone with the adventurers off visiting their families and sharing what little plunder they've been able to sneak past the guardian's long-reaching grasp).
Maybe, just maybe, a new adventure has surfaced to provide you with some entertainment of a slightly different flavor. Here is a taste...
***** Blergh's 2E D&D Game *****
DM: All of you awaken to find yourselves lying on the western bank of a wide river, hands bound tightly in front of you. About 30 yards away, you spy an old row boat pulled up on the shore. Off to the west, high chalky cliffs rise up above you.
Stomper the Ranger: As I make my way over to the row boat to search it for anything useful, I'll scan the ground for any flint-like rocks large enough to break and create an edge sharp enough to help cut someone out of their bonds.
DM: Roll a Survival check please.
Stomper: [rolls] Umm... dang. Heck of a time to roll a 20.
DM: You don't find anything. Do you want to keep looking?
Stomper: It's either that or I try to gnaw the ropes off, so I guess I'll keep looking. [rolls] Ok, this time I got a 10.
DM: After 10 minutes, you finally find a suitable rock and fracture it to create a sharp edge. Whose bonds do you want to use it on?
Stomper: [since he doesn't know any of the other people in the party yet] I randomly select Player 1's character.
DM: Ok, please roll for an attack and damage.
Stomper: Oh, crap, who are we fighting?? Wait... you mean to cut the ropes with a suitably-sharp rock?