I kept hearing this song called "Since You've Been Gone"
on classic rock radio and thought it was probably by REO Speedwagon or something. It turns out it was actually Rainbow - the much poppier sound and non-Dio vocalist threw me off a lot.
When I first heard Kill Hannah's "Kennedy"
on the radio I thought it was a new Garbage song. The weird part is that Kill Hannah doesn't even have a female vocalist.
edited 5th Sep '11 11:42:30 AM by MikeK
It was mainly the names, but I remember how at first I didn't know the difference between The Who and The Guess Who. I think even once I started sorting out who was who * , I was somewhat clinging to the idea that there was some sort of connection between the two beyond similar names.

Are there any songs that you had mistakenly thought were sung by a differeng singer than the one that actually sung them?
For the longest time, I thought that Christina Aguilera did Evacuate The Dance Floor.
At first I didn't realize I needed all this stuff...