Everyone speaks the common tongue here 
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Rhyming is def region based. Theres no official rhymes between words.
Where I live, the words Bad and Mad Rhyme, and Sad and Dad rhyme, but bad doesn't rhyme with sad, nor mad wth dad. Glad rhymes with mad and bad but not with the glad in gladiator, which rhymes with sad and dad. We have what is called a split short A system, and its one of the hardest dialects for an actor to actually mimic. This is why they are basically forced to cast Tina Fey to do it 
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Edit: 
https://m.youtube.com/watch?v=QLDjE33_uRM