The YouTuber, who is the first social media star to take part in the show, was seen making The Circle gesture as first couple Danny John-Jules and Amy Dowden got their scores and later behind Seann Walsh and Katya Jones.
The game has a player make a circle gesture with their hands below their waist and if another person looks at it, they get punched in the arm.
And it seems the 27-year-old couldn’t resist slipping the viral game into the opening show of series 16 - something that didn’t go unnoticed by viewers.
— Katie P-H (@harripound) 22 September 2018
One wrote: “@Joe_Sugg doing the circle game on strictly had me dead! #Strictly #strictly2018.”
While another said: “Anyone else notice that @Joe_Sugg is playing the circle game? #strictly @bbcstrictly.”
— Joanne Kirkbright-Burchall (@YTJoanneKB) 22 September 2018
— Katie whelan (@k4k8e) 22 September 2018
— romany loves lucy 🐝 (@sdmncabello) 22 September 2018
— J // (@jxxooa) 22 September 2018
— ida ◟̽◞̽ (@0RCHIDLOUIS) 22 September 2018
“Joe i see you doing the ok gesture you cheeky one @Joe_Sugg #strictly,” laughed somebody else.
But not everyone knew what Sugg was doing, with many wondering what his gesture was all about.
Somebody commented: “#Strictly what’s with the hand signal Joe?”
“What is @Joe_Sugg doing in the background??? #Strictly,” asked a different user.
Sugg scored 27 for his Jive, the penultimate dance of the first show, with three seven's and a six from Craig Revel Horwood.
— BBC Strictly✨ (@bbcstrictly) 22 September 2018
He wore glittery silver trainers for his jive to Take On Me by A-Ha, which saw emojis projected over the dancefloor as he spun partner Dianne Buswell around.
Bruno Tonioli told him that he was "moving in the right direction" while Revel Horwood said that he did "not have high hope" after the launch show but his routine "changed everything".
Bussell described him as "a Mexican jumping bean", while Ballas referenced her predecessor as head judge, Len Goodman, when she told him: "You gave it some welly, as Len would say."
But it was Pussycat Dolls star Ashley Roberts and Steps singer Faye Tozer who rocketed to the top of the leaderboard after impressing with their Strictly Come Dancing debuts.
They both scored 29 out of a possible 40 in the first week of the competition while What Not To Wear presenter Susannah Constantine languished at the bottom of the rankings with a score of 12.
Roberts was cheered on by her bandmate Kimberly Wyatt for her Viennese waltz to Perfect by Ed Sheeran featuring Beyonce with partner Pasha Kovalev.
Head judge Shirley Ballas told her she showed "a beautiful musical ear, so feminine", while Bruno Tonioli said the dance was "all seamlessly beautiful" and Craig Revel Horwood said: "The whole thing was gorgeous."
Steps singer Faye Tozer was the last of 15 celebrities to take to the dancefloor for the first live show of the BBC One series.
She performed a cha cha cha to Lullaby by Sigala featuring Paloma Faith with her partner Giovanni Pernice.
Revel Horwood praised her, saying it was "most certainly worth the wait and by no means a tragedy darling. It's amazing what you're doing week one".
The judges were less impressed with Constantine, who appeared with a large bowl of fruit on her head at the start of her samba to Tico Tico by Carmen Miranda.
Her partner Anton Du Beke emerged from under her large skirts to start the routine, before the huge dress was lifted up to the ceiling and Constantine was revealed to be wearing a much shorter ensemble for the dance.
Afterwards, Tonioli said: "I'm glad it's over. It was more like Car Crash Miranda than Carmen Miranda."
Revel Horwood said she looked like she was "staggering about lost and drunk at a party, the best part was when you fell on the floor at the end", prompting Constantine to ask him: "Will you come and show me how to do a few steps?"
Darcey Bussell told her: "I like a bit of comedy but I've seen you work hard and I know there is a dancer in you, I know the promise of you dancing is great, you don't need any props."
Revel Horwood disappointed the duo by awarding them just one point, while Bussell and Tonioli gave them four and Ballas gave them three.
However, they have avoided the threat of elimination this week because nobody will leave the competition until next weekend, when their scores are added to next week's totals.
Broadcaster Stacey Dooley became the first contestant to attempt a quickstep in the first week of the competition.
She took to the floor with partner Kevin Clifton to Dancing by Kylie Minogue.
Afterwards, Revel Horwood told her: "I enjoyed every minute, for someone who puts her life at risk in documentaries, to come out with all that glamour with the hardest dance in week one, you did very well."
They received a score of six from all four judges for a total of 24.
Also impressing the judges were Red Dwarf star Danny John-Jules and This Morning star Dr Ranj Singh, who all came joint second with 27 points.
The This Morning doctor wore a white coat and a stethoscope for the start of his cha cha cha to How Will I Know by Whitney Houston.
He ripped off the coat to reveal a bright yellow silk shirt for the energetic routine with partner Janette Manrara, which earned him a standing ovation from Ballas.
Other stars to show off their first routines were Blue singer Lee Ryan, TV presenter and campaigner Katie Piper, newsreader Kate Silverton, radio DJ Vick Hope and Paralympic champion Lauren Steadman.
Rounding off this year's famous hopefuls were Casualty actor Charles Venn and cricketer Graeme Swann, while comedian Seann Walsh delighted the audience with his tango inspired by the BBC One hit drama Bodyguard.
The public vote will begin in the second week of the competition.
Strictly Come Dancing continues on BBC One at 6.15pm on Saturday.