I've always wanted to know who could win a Table Tennis match between Shadow and Luigi, and now I can finally find out!
Winter Olympics had a special "Spot the VIP" goal at certain points, where a character wrote to you, telling you to keep an eye out for them at a certain event. One of these characters is Chaos.
London 2012 Olympics had the Dream Hurdles on a rotating platform from Battlerock Galaxy. When it speeds up, so does the music. The rotation does have a max speed, but by then, the music will be broken.
The rivals from the Winter Olympics come back for London 2012. Dry Bowser's event? Dream Long Jump.
The plot of the DS version of Winter reveals that Vector ditched his work and joined the Olympics while Espio and Charmy are still doing their job, and they call him out on it. Even better, this is arguably true for every game in the series.
Luigi breakdancing when he gets 1st place: hilarious. Luigi breakdancing after beating Sonic and Shadow at a speed match: priceless.