[THE most famous? The next time Bart runs into Clark, there are going to be words. Mainly words about how come Impulse was nowhere near as famous, but words all the same.]
'Cause that's the kind of guy he is. He's a fantastic friend, but when he's saving cats and old ladies and probably the world, the media takes notice.
If your world has Superman comics books, they've gotta have a Superman too, right?