Haruka makes good のワの faces in Agent Yoru wo Yuku, too.
And actually, I don't think this was mentioned yet, though it's a basic one. In "GO MY WAY!!", on the line "dakara dare mo ga yume wo miteru", Yayoi says "miteru" differently (more like "mitere~e").
I tend to forget this when I'm making things in L4U and it stands out if I have the other idols sing that line as well...XD
Also, I don't know if this counts, or if I even have it right, but in remix A of Ohayou!!Asagohan, there's an "mmm!" at the end of the song in the BGM if you have Haruka somewhere in your unit.