I'm not sure how someone who talks that hip wouldn't be recognized on the phone, either.

The hero going temporarily bad without even realizing it...is a pretty common Silver Age comic plot. Often it's the result of red Kryptonite, or a head injury, or exposure to chemicals, or in today's case, an element man's cure in chemical glop. From 1973's World's Finest Comics #219, "Tick Tick Boom Boom" Written by Bob Haney, art by John Calnan. A weird-sounding voice calls in bomb threats to Simon Stagg's bus terminal and park; and while Rex jokes there's a million people who would love to see Stagg blown to kingdom come, it's an unhinged and amnesiac Metamorpho leaving the bombs!

Stagg says Metamorpho's split personality is the result of the "glop cure" he put him in...I don't know either. Still, another dose cures Rex, but he doesn't remember where he planted his last bomb in Stagg's skyscraper, which could blow up with Sapphire in it! Although he saves Saphh and the building, the issue closes with another bomber calling in a threat to Stagg's yacht, which doesn't seem to be the laugh riot you'd expect. It occurs to me Metamorpho's good personality could've been planting the bombs, and his evil half defusing them: Stagg is that bad, people.