Even smarter casual
Sometimes even customers are impressed by a bit of dress lateral thinking instead of suited convention. At a conference/exhibition in Anaheim (ugh...) a couple of years ago we were all getting a bit squirrelly after three 10-hour days of back-to-back meetings, and coming back from dinner we passed the Disney shop...
When the first customer turned up to the meeting next morning they saw everyone sitting around the table with laptops as normal. Except for the Mickey Mouse ears (Minnie Mouse bow for the gals). And the presenter using big white Goofy hands to point at the screen (try counting to four in those). As the tech guru I was wearing a wizard's hat, with flashing lights on -- and as became obvious when I got up and walked across to drive the hardware demo, big yellow furry shoes.
The MD of the customer insisted on having his photo taken with us as we shook hands on the deal, so it can't have made such a bad impression. Almost certainly the best $200 worth of expenses the company ever paid for :-)