On my Mac Book Air, Messages looks just like it does in the videos of it and very similar to the iPad and iPhone interface. On my iMac, there are a handful of odd / different things about the interface: 1 - Text appears over a much flatter, matte looking background rather than the bubble background. 2 - The text stretches all the way from the right side of the available space to the left (rather than only being about 2/3 of the available width.) 3 - Pictures appear on the left side of the screen, regardless of who sent the message (rather than the picture of me appearing on the right side of the screen.) 4 - There's no tail on the messages to indicate which person was talking. 5 - Rather than displaying the ••• symbol to show someone is typing, it shows a text message of "..." - something people actually send sometimes, so it's confusing whether they actually sent three dots or are in the process of typing something. How can I change the interface on my iMac so it matches with my MBA? Edit: Found it! It's hidden in a very non obvious spot. You'd think it'd be in the preferences window, like everything else, but instead it's in: "View -> Messages -> Show as Balloons"