Before the Hoops' 4-0 SPL win over Dundee United at Parkhead on Tuesday night - in which the former Scunthorpe striker scored his second brace in four days to take his tally for the season to 22 - manager Neil Lennon confirmed Hooper had rejected a contract offer.
He also revealed Celtic had turned down another, barely improved, offer from the Canaries after rejecting a bid last week, reported to be about £5million, for the 24-year-old who has 18 months left on his current deal.
Asked if the Norwich bid was derisory, in light of the money that is swirling around the Premier league, Mulgrew, who played at Wolves, said: "Of course. We see him day in, day out and we know his quality, what he can do, and you see the goals he scores. So, yes, I think he is worth a lot more than that.
"He is a big player for us and we want to keep everyone.
"There is a good squad here. We all get on well and there is a good team spirit so we don't want to lose anybody.
"Maybe Gary is thriving on it (speculation) but he has been a good player for us all season before the speculation began. He is a great player and he's showing that just now.
"He is a good lad. He doesn't let it get to his head. He gets on with his job and you've seen that last night and on Saturday."
Celtic's convincing win over United took them 12 points clear of Inverness at the top of the SPL and kept the momentum building ahead of next month's Champions League last-16 clash with Juventus.
However, in time-honoured way, Mulgrew is taking it one game at a time as he turns his attention to the Scottish Communities League Cup semi-final against St Mirren at Hampden on Sunday.
The former Aberdeen player said: "I think it is about consistency and the last two performances have been good. We kept a clean sheet against Dundee United and scored goals so that is positive.
"We look towards Sunday now. We are not looking as far as Juventus yet.
"We need to put that to the back of our head and concentrate on doing the job against St Mirren first, get the domestic stuff right and deal with Juventus when it comes."
Further goals from midfielder Victor Wanyama and substitute Scott Brown gave a deserved sheen to the scoreline for the impressive champions.
Gary Mackay-Steven missed an early chance for the visitors which he admits might have cost his side dearly but the United wide-man is looking to make amends against Ross County at the weekend.
"I think that is the beauty of football - you have good games and bad games but there is always a game soon after where you can put bad games right," he said.
"So we will get this game out of our system, regroup and look forward to Ross County at home and look forward to getting back to winning ways.
"I had a great chance and I should have done better.
"I maybe should have taken the ball on to my left and opened it up but I put it on to my right and put it past the post. It is just one of things and it maybe cost us in the end.
"Maybe I had too much time and maybe it would have been a different game but I was a bit unlucky and in the end Celtic showed their class.
"When you look at Gary Hooper, (Georgios) Samaras, and people like that, they take chances like they did last night and it all comes down to goals in the end.
"So we will be looking to be more clinical."