But the Lions' next opponents are in no mood to join the celebrations and will be aiming to wreck Williams' day in a repeat of the World Cup Bronze Medal Final which the Wallabies won 21-18.
"Shane deserves a fairytale ending but we will be doing our best to spoil that. We want to gatecrash his party," said Australia flanker David Pocock.
"When you think of Welsh rugby it's very hard not to think of Shane Williams making defences look silly with his sidestep, his pure speed and ability to sniff out a try.
"There will be a lot of front-rowers breathing a sigh of relief after he hangs his boots up on Saturday."
Versatile back James O'Connor started at fly-half in the rout of the Barbarians last Saturday and will hold on to the No10 jersey against Wales.
And the Rebels-bound star admits he used to study Williams when he initially made the switch from playmaker to his now more customary role of wing in the early stages of his professional career.
"I always prided myself on playing 10 or 12 but as soon as I moved to wing I watched Shane's game quite a bit - just the way he gets around the field and gets involved," said O'Connor.
"Coming over for my first tour with Australia I watched the boys play and Shane just cut us apart. He was coming in at second receiver and just chopping people up. I remember watching that and trying to bring it into my game.
"I've marked him a couple of times and I can say from experience that he's one of the most gifted athletes around. He's similar in stature to me, he's a quick man, with great footwork and has enjoyed one of the best and longest careers around."
The clash in Cardiff is the second occasion Wales have faced Australia this year and Warren Gatland's men also travel Down Under for a three-Test summer tour. And O'Connor is relishing locking horns with Wales again as the Wallabies look to finish their season on a high.
"Wales played some of the best rugby at the World Cup. They have a good style and it will be quite a spectacle," added O'Connor.
"We played each other in the third-place play-off at the World Cup and that was pretty exciting. Being Shane Williams' final game will make it that much more special.
"I wouldn't say it's a friendly match - this is the game of our tour. I expect a bit of a backlash but we really want to win this game to finish our year on a high."
Australia (vs Wales, Millennium Stadium, Saturday, 2.30pm)
Adam Ashley-Cooper (NSW Waratahs); Lachie Turner (NSW Waratahs), Rob Horne (NSW Waratahs), Berrick Barnes (NSW Waratahs), Digby Ioane (Queensland Reds); James O'Connor (Melbourne Rebels), Will Genia (Queensland Reds); James Slipper (Queensland Reds), Tatafu Polota Nau (NSW Waratahs), Salesi Ma'afu (Western Force), James Horwill (Queensland Reds, capt), Rob Simmons (Queensland Reds), Scott Higginbotham (Queensland Reds), David Pocock (Western Force), Ben McCalman (Western Force)
Replacements:Stephen Moore (Brumbies), Ben Alexander (Brumbies), Nathan Sharpe (Western Force), Radike Samo (Queensland Reds), Ben Lucas (Queensland Reds), Ben Tapuai (Queensland Reds), Anthony Fainga'a (Queensland Reds)