Yes, Follow-up songs and Answer songs are often two different things. Answer songs, for example, are often by different artists.
Well, if you were listening to "50s on 5" on XM/Sirius yesterday afternoon, you may have heard one I never knew about.
Have any of you ever heard the follow-up and answer song to "Papa-Oom-Mow-Mow" by the Rivingtons? I never had before. And confirmed my suspicion: CFUN never charted it, so they probably never played it.