I don't think it's a glitch, and I don't think our individual parents are behind the couch as my parent wasn't the one sticking his little head out. And I get the couch every time, so it's not just the first time you log on.
I think the reason bandai made it a couch was so it was "universal" for everyone. I don't think they had the time/energy to make sure each specific parent shows up in tamatown. Just as our own personal tamas don't show up when we play certain games (like clean up or tennis). That's just my observation/opinion, though.