"You're drastically downplaying the similarities to Living Single, but even if it was just the basic concept, that still makes it derivative, by definition."

One of the issues with this argument is that nothing much of Living Single was original, either. The free floating cast of peers had been long established by Seinfeld and even shows like The Golden Girls. The long-running romances come from Cheers and multiple clones. One show can't be said to copy another if they both just trace back to common ancestors.