Because they actually remembered "Hey Jude"! It's the song that Dean and Sam's MOM sang to them!<<<I think the song O' Death by Jen Titsu or someone should be on there! That's Death's entrance song and I love it!
My theory is Dean Winchester is bisexual, but maybe not for Castiel especially just guys in general. Sure, that's fine if Destial is your thing, but maybe Dean just enjoys guys and girls. Just not particularly Cas.