Few could have foreseen the giant centre-back becoming such a popular figure when he arrived during a flurry of late transfer activity in August 2011.
While the likes of Park Chu-young and Andre Santos flopped, Mertesacker recovered from a difficult first season in north London to establish himself as a key member of the side.
That defensive quality alongside his manner has seen the 29-year-old embraced by Gunners fans, whose chants of 'Big F****** German' will no doubt echo around Wembley when Arsenal take on Hull in the FA Cup final on Saturday.
"I was frightened at the start because the 'F' word, you cant say that on tele or somewhere else," he said of the chant that is done to the tune of The Sandpipers' Guantanamera.
"It was always a bit weird
A German journalist told me 'they quite like you'
My first impression on that was not good but finally I got it."
Mertesacker has now embraced the nickname - so much so that he is using it for good, selling BFG T-shirts to raise money for his charity, which supports socially disadvantaged children in Hannover by encouraging them to take up sport.
"It worked really well, we just keep on going with that to try to raise some money for my foundation," he said of the Per-Mertesacker-Stiftung.
"It is a good thing together with my chant
Credit to the fans."
That support helped Mertesacker overcome his difficult start to life in England and still gees him on now.
Speaking of the fans, the German, in his understated way, said "it looks like we like each other" and wants to reward them at Wembley this weekend.
"It would mean a lot, that would be a big step for our team as well," he said
"We went through a lot of difficulties.
"We were top of the league, then we dropped points and then came back to fourth position
We want to keep our run now.
"We won five consecutive games, we want to continue with that (on) Saturday
That is really important
It looks like we are back on track
We have to keep our focus."
Mertesacker will be cheered on at Wembley by friends and family, including brother Timo who bears a striking resemblance to the defender and has a penchant for going on Arsenal away trips.
"He does it just to improve his English and get on with away fans," he said
"It's a good experience to get.
"He just loves it and, when he has time, he comes over just for away games."
Mertesacker's friends and family will be hoping to see the giant defender collect his first silverware in five years this weekend.
He missed Werder Bremen's German Cup success in 2009 through injury but still took home a medal thanks to the decisive goal from Mesut Ozil.
The Germany internationals are obviously now plying their trade together again in north London, where the playmaker is beginning to impress once more after a mid-season slump.
"We are happy that we have him back in our squad and available because you could see from the start that he is one of the best players in Europe," Mertesacker said.
"His contribution and his assists are vital for any club, so we are happy to have him back.
"I knew before he would suffer at some moment in his first Premier League season, so we are happy that he is fit again and that he has got a few games under his belt to go now to Wembley and show everything."
Source : PA