In its 11-season run, Frasier featured a number of impressive celebrity voice cameos—from John Lithgow to the great Mel Brooks—but the story behind them highlights just what makes them so perfect. In the Cheers spin-off, the titular psychiatrist hosts his own radio show, on which he offers his professional advice to his listeners. Frasier's radio show takes calls from people who need more specific advice, and this is where many of the show's celebrity cameos came in.
One of the show's best running jokes was Frasier's celebrity cameos, which were incredibly easy to miss. These appearances came in the form of individuals calling into Frasier's radio show, often with unusual problems or abrasive personalities for added comedic effect. However, what made these cameos so perfect goes far deeper than the simple fact of their existence or their regular recurrence.
What makes Frasier's celebrity voice cameos work so perfectly actually stems from the story behind how they were captured and the nature of how they were written into the show. The format of the cameos made for a satisfying running gag, with fans attempting to identify the celebrity by just their voice, but the fact that the celebrities never actually appeared on Frasier made it all the more satisfying. Put simply, Frasier's high number of cameos avoided being seen as a gimmick because of how subtly they were achieved.
The show's use of the celebrity cameos through phone calls actually made them much easier to record. Usually, the callers' dialogue would be read off-camera, and the celebrities' voices would then be added in post-production. This allowed Frasier's celebrity guest stars to record their dialogue over the phone, which actually made the variety in cameos much easier to achieve, as none of the celebrities needed to be physically available to film their cameo - a simple phone conversation was never a constraint on their time.
By making the celebrity cameos part of the titular character's radio show, the show's writers were also able to link them to Frasier's original premise. This allowed the cameos to feel organic, rather than forced, making them a subtle running gag which highlighted Frasier's more sophisticated sense of humor. Many of the celebrities even disguised their voices for their cameos, making it even less obvious exactly whose voice was being heard in any given episode.
All of Frasier's celebrity voices were thanked at the end of each season with a "thanks for calling" montage, showing the names and faces of the actors who had taken part. This was a perfect way to reveal the extent of Frasier's cameos without breaking the show's carefully written subtlety, also confirming or disproving fans' identifications of the voices throughout the season. Whether or not Frasier's upcoming reboot will find some way of reusing the old method of obtaining impressive and subtle celebrity voice cameos remains to be seen, but it was certainly one of Frasier's greatest running gags.