The 22-year-old midfielder joined his international team-mates on the training pitch in Malahide on Tuesday morning just hours after completing a deadline-day switch from Wigan to Goodison Park.
His price-tag, an initial £13million plus add-ons, made him the most expensive Scottish-born footballer ever, a title which previously belonged to injured Ireland colleague and fellow Glaswegian Aiden McGeady.
However, McCarthy is adamant neither the fee nor his place in Scotland's football history will weigh heavily on him.
He said: "No, not at all. I am looking forward to it. It's a new challenge and as I say, I am really looking forward to it.
"I have had a few people on my case about it, and it's one I'm going to need to take in my stride.
"Hopefully I can make the step up to a big club at Everton, and it's one I'm looking forward to.
"Players go for all different kinds of money these days. I'm just delighted to be an Everton player.
"Obviously I am delighted to be back in the Premier League. It's a real excitement and a new challenge for myself."
The chance to work under Toffees boss Roberto Martinez once again - the pair spent four years together at Wigan - proved attractive.
However, McCarthy has been told to expect no favours as he prepares for the latest phase of his career.
He said: "It's brilliant. I have worked under him [Martinez] for four years and he's a great manager.
"It's not going to be easy. Obviously, I need to work hard - I have been told by his staff I have to get my head down on and off the pitch, but I am looking forward to the challenge."
McCarthy's mood might have been very different had he suffered a similar fate to Ireland team-mate and West Brom striker Shane Long, who flew back to England on Monday night as Hull attempted to push through a late deal for him.
Long ultimately flew back across the Irish Sea with his situation unchanged, and the midfielder admitted he at times feared he might be doing the same as his transfer - which was all tied in with Marouane Fellaini's departure from Everton for Manchester United - went right down to the wire.
Asked if he thought it might not go through, he said: "At times during the day. My agent was sitting with me and it was frustrating for both of us.
"It was hectic. It wasn't nice to be waiting about, especially as it took until 10.50pm when we got confirmation that it was going to happen.
"It was just a relief, to be honest, and such an excitement to go to such a brilliant place like Everton."
For the next week or so, McCarthy will have to put his excitement to one side and turn his attention to the task of helping Giovanni Trapattoni's men make a potentially decisive move in their qualifying campaign.
Victory over Sweden in Dublin on Friday followed by a repeat in Austria on Tuesday would give them every chance of claiming the runners-up spot in Group C and a berth in the play-offs for the finals in Brazil next summer.
By the same token, defeat in either game could prove fatal with all three teams currently sitting on 11 points.
Trapattoni has set a minimum target of four points from the two games, but McCarthy knows just how important collecting three of them at the first attempt could prove to be.
He said: "The main thing is getting the three points against Sweden and then go to Austria.
"We will take it one game at a time, but there is a real buzz about the camp."
Whatever happens over the next week or so, McCarthy will begin a new adventure on his return with at least one of his Ireland team-mates taking a particular interest.
Stoke striker Jon Walters is an Everton fan and has already marked the youngster's card.
McCarthy said with a smile: "I spoke to Jonny and he is delighted that I am there. He has just told me to get my head down and work hard now."