That reminds me of a "Palace of the Silver Princess" (old D&D) adventure I once ran...
A group of experienced (A)D&D-players found the summoning circle and thought it might be nice to call out for Bahamut...
After several unsuccessful (I don't know why, but I granted them a 1% chance that it MIGHT work) tries they got bored and tried to summon Orcus...
And guess what: He appeared !!
After a slight shock of the PCs (they were levels 2-3 at max) and some examination (OK, orcus certainly doesnt have an "detect low level" ability, but he should have the experience to dfind the group's relative power level) Orcus decided to "play a joke" on them...
He bowed his head and asked: "What is it that you wish for ?"
Some more shock from the group... but one (inspired by munchkinlike dreams) called out "give us you wand!"
Orcus (knowing that they wil never survive the contact with it) thought "what the heck" and threw it to the PCs...
Just then it dawned to them that they couldn't touch it and tried to dodge it... I was very nice and allowed everyone a Dex-check...
Orcus then asked if there was anything else and they thought to dismiss him... He vanished (invisibility or whatever) and had some fun with the group... levitating the wand around and zooming it through the room...
It all ended with them summoning him another time and making a deal with him... He would take his wand back and they would make themselves useful to him someday...
