Joey Barton's side were 12th in League Two when Anderson joined them on loan at the end of January, but had climbed the table thanks in no small part to the 19-year-old's performances, goals and assists.
Even so, they needed to better Northampton Town's result by five goals to overtake them in third place, and the Cobblers were 3-0 up inside the opening 22 minutes in their fixture at Barrow.
Bristol Rovers, meanwhile, scored two first half goals in their home game against Scunthorpe - but went nap in the second period, and with Barrow pulling one goal back and the Gas winning 6-0 with five minutes left on the clock, they knew that one more goal would be enough to send them up.
And fittingly, it was Anderson who sent them into seventh heaven with his eighth goal of the campaign, a late header which sparked a pitch invasion that led to a lengthy delay. But play eventually resumed, and Barton's men played out the game to seal promotion.
Anderson, who earlier in the day had been named as the EFL Young Player of the Month for April, played the full match in what was his 21st appearance for the club, also claiming assists for the opening two goals, and he will return to Newcastle having written his name into Bristol Rovers folklore.
Northampton will now have to navigate the play-offs, where they will come up against Mansfield Town over two legs after Matty Longstaff helped the Stags book their place in the semi-finals. His sixth goal of the season opened the scoring against Forest Green, and a final score of 2-2 meant that Nigel Clough's side finished seventh - one point ahead of Sutton - and Forest Green won the title on goal difference.
Also celebrating were AFC Bournemouth, who clinched promotion back to the Premier League during the week and rounded off their Championship campaign with 1-0 victory over Millwall on Saturday, but Freddie Woodman was an unused substitute.
Jeff Hendrick wasn't involved as Queens Park Rangers beat Swansea 1-0 while Joe White didn't feature for Hartlepool United as they ended their League Two season with a 2-0 home defeat to Colchester.
