Petr Cech was given a warm welcome to Arsenal by his new team-mates - although Theo Walcott could not resist a cheeky dig.
The 33-year-old on Monday completed his move from Chelsea, ending his 11-year stay at Stamford Bridge.
" Scored my first ever arsenal goal against him - delighted to welcome @PetrCech to @Arsenal !!! #WelcomeCech," Walcott wrote on Twitter, also posting a picture of the goal in question.
Gunners midfielder Aaron Ramsey hailed Arsene Wenger's latest recruit as one of the best goalkeepers the Premier League has had, tweeting: " Wow what a signing! One of the best @premierleague keepers ever! Welcome @PetrCech."
And Mesut Ozil said on Twitter: " From blue to red - welcome @PetrCech to the @Arsenal family! #YaGunnersYa #AFC #COYG #WelcomeCech."
Former Arsenal striker Ian Wright thanked Chelsea boss Jose Mourinho for allowing Cech to move to a rival Premier League club.
Speaking to BreatheSport, he said: 'I am absolutely delighted for Arsenal and, as a fan, I couldn't be happier. We finally have a world class stopper. Thank you Jose!"
Wojciech Szczesny, whose place in the Arsenal team Cech is set to take, also welcomed the new signing with a post on his Facebook page.
"Petr Cech, welcome to Arsenal FC! Delighted to have a chance to learn from one of the best GK's in the world!" the Pole wrote.
Former Arsenal goalkeeper David Seaman said Chelsea could live to rue letting Cech move across London.
"Chelsea's loss could, and likely will, be Arsenal's gain. In my opinion this signing could genuinely be the difference between who will come first and who will come second next season," he said on BreatheSport.