Dream events also return, splicing sports with Nintendo and Sega DNA to create Mario Party-ish bursts of fun. Hurdles becomes a frantic conveyor belt dash in Battlerock Galaxy, uneven bars plays out in Sonic's futuristic Celia City, and the discus itself is ridden round Green Hill Zone.
Some are better than others (see the 'Dream A Little...' box, above), but there's a nice mix of selfish solo efforts and team-based co-operation. Getting four players to steer a raft down Cheep Cheep River is a particular hoot. More co-op events in Rio 2016, please! (With sales figure like M&S's, you know it's going to happen.)
The usual complaint that dream events show up the 'realistic' events doesn't apply here. Sega pump real world disciplines with more gimmicks and arcadey guff than before. There are special attacks, flaming bursts of speed and glittering star trails from perfect jumps - as there should be.
In the past, we've always sensed Sega shying away from their natural excessiveness in an attempt to appease their Olympic licenser - for the first time they've shown you can pay homage and keep tongue in cheek.
All the various bits are held together in London Party mode. It's a Mario Party-esque contest where contestants trot around a model village London looking for events and with them the chance to win stickers. Bumping into Mario and Sonic characters triggers minigames independent of the main events - coin-grabbing, maze-exploring, Boo-escaping bits of fluff.
When Big Ben tolls, everyone is pulled into a sporting event to compete for a big prize. It brings together London 2012's disparate parts quite nicely, and certainly trundles along faster than Mario's board game bore-a-thon.
London Party doesn't hold up half as well for single players, and they might miss having a dedicated mode of their own. Winter Olympics weaved the events into a 16-day replica of the event - would it have been too much to throw in similar cladding here? Instead players make do with challenges, a series of Xbox-y achievements awarded for chains of perfect hurdle jumps or besting events with different characters. Many are challenges you'd be doing anyway if you wanted a shot at the online leaderboard, so it does feel a little superfluous.
That said, Wii already has two hulking solo adventures for Christmas: Skyward Sword and Xenoblade. Mario & Sonic fills the multiplayer gap, and does it with good-humoured minigames and a renewed focus on throwaway Olympic fun. As far as party games go, it's the gold standard.
Got loads of friends and a high tolerance for Sonic's crappy entourage? This is the party game for you. Loners are best off finding their fun elsewhere.