Mohamed Elyounoussi revealed he surprised Norway team-mate Kristoffer Ajer by turning up to sign for Celtic without telling him.
The on-loan Southampton winger sought advice from Saints team-mate Stuart Armstrong about life in Glasgow but decided to leave Ajer alone to deal with football matters.
He said on the Celtic website: "It was more of a surprise for Kristoffer because I didn't talk to him before I signed.
"I didn't want to bother him since the team were preparing for the play-off game against AIK. In the end, I had heard enough to convince me to come here anyway, but now that I'm at Celtic it's good to talk to him about it.
"I'm proud to be part of the club, to come here and I'm looking forward to the season. Celtic is a massive club with a lot of fans, and I like the challenge of trying to win games and win titles."
The 25-year-old could make his debut in Sunday's clash with Rangers at Ibrox in what is an eagerly-awaited contest between two form teams.
But Celtic manager Neil Lennon has rubbished talk of the derby meeting setting a marker for the title race.
Both Celtic and Rangers have won their opening three games and qualified for the Europa League group stages ahead of their meeting at Ibrox on Saturday.
But Lennon believes it is too early to read much into the outcome of the derby.
"That's just rubbish all that talk," he said. "It's the fourth game of the season. There's another 34 to go after that.
"You can ask me that maybe around February/March when we will have some sort of idea of where we are in the table. But after four games...
"We get too hysterical too early and it's almost game by game, every performance gets analysed to death.
"To say it's a marker, a defining moment in the season, sorry I'm not buying into that talk."
Lennon claims a goalless encounter would not necessarily be a surprise.
"It would and then it wouldn't because you can't predict these games," he said.
"I'd be delighted to keep a clean sheet. I'd fancy our chances to nick a goal or two.
"There's a lot of positive contributions in the goal stakes from a lot of areas and we scored from a set play on Thursday night, which delighted me.
"We have scored nine in the last three games so that is good form by any standard."
