Sudden speech attempts

My son in the last 2 weeks has started copying EVERY word and action of his tv shows. This has literally come from no where (coincidentally it started very soon after starting melatonin, whether that makes a difference is anyones guess!). Now his pronunciation is no where near what it should be, and it's basically just the beginning of the word or first syllable. Has this happened with anyone else where the word attempts came on suddenly and how did it evolve from there? He's 3.5 for context!