The Monkees, for me. They started out as teenyboppers until they (led by Nesmith) asserted themselves and moved in a more progressive (though not as commercially successful) direction. I don't think The Beatles can accurately be described as teenyboppers. From the very start they wrote most of their own music, and their early compositions were well-reviewed at the time by the Classical Music Reviewer for The London Standard (or whatever the main London newspaper was). They may have appealed to a lot of pre-teens and teens, but that does not a teenybopper band make, IMO. .