The Wales star, who toured South Africa with the Lions in 2009, is one of three former tourist in the Barbarians squad for the June 1, Hong Kong clash.
He was disappointed to miss the cut for selection for the Lions' 10-match tour but is honoured to add the famous invitational club to his glittering rugby CV.
"I was always hoping I had a chance but I suppose it comes down to the fact that I have not played a lot of rugby for Wales in the last year or two," said Hook.
"I feel I could have done a job for the Lions but I was always on the back-foot - it's each to their own. It's up to me to knuckle down and work hard on my weaknesses, which is something I will always do.
"But I'm really looking forward to facing them.
"Playing for the Barbarians is something I've always wanted to do. It's one of the only things I haven't done - I've played in the World Cup, gone on a Lions tour but never played for the Baa-Baas.
"It's a great honour so I'm chuffed with the invitation to play with so many great players."
The Lions and Barbarians are two of the most recognisable brands in world rugby and Hook grew up watching videos of the famous duo.
The Hong Kong Stadium clash will be the first time the two sides have met and the Perpignan fly-half is well aware of the match's historical significane.
"There's so much culture and history with the Barbarians," said Hook.
"I've grown up watching videos of their games with my grand parents. To play for the Baa-Baas is great and my family are thrilled as well,
"Every Baa-Baas player across the board stands out. I've played against a lot of them and with a few of the Welsh boys.
"It's going to be such a huge match and is brilliant for the fans, I'm sure it's being eagerly anticipated all over the world."
It will no doubt be a formidable match for the Lions to kick-off their tour and Hook reckons the Baa-Baas can cause an upset.
"Warren has already mentioned that it is all about the Test matches on a Lions tour," said Hook.
"You can win all the warm up matches but if you lose the Tests, that is what the fans remember.
"But this is a really hard game for the Lions to kick-off with.
"If you look at the teams on paper there's not much between them at all. All the players in the Baa-Baas squad are top class and have been there and done it."
With a host of English and Irish player involved in domestic finals, Gatland is likely to pick a very Welsh influenced side to take on the Baa-Baas.
Hook admits it will be a surreal experience and is expecting a torrent of banter to come flying his way from the likes of former Ospreys half-back partner Mike Phillips.
"There will be a lot of Welsh boys involved in that game and personally that will be very strange," added Hook.
"Mike's always full of the banter but he's a good guy and one of my best mates. I've played against him a few times in France now so I'm used to it."