I get a kick out of the disconnected-phone gags in the Simpsons. They're not all that common, but they're pretty funny. Two that come to mind immediately are:
"[Dee dee dee] We're sorry, but the fingers you have used to dial are - too fat. To order a special dialing wand, please mash the keypad with your palm." (From the Fat Homer episode)
"[Dee dee dee] We're sorry, but the number you have dialed cannot be reached from this phone. You. Negligent. Monster." (From the Neglectarino episode)
Heh heh.
ff