Newcastle were seeking their own place in the record books after thumping Olympiakos 4-0 in the UEFA cup in midweek to register their eighth straight win. But lifelong Magpies fan Stone had other ideas and was ideally placed to equalise on the stroke of half-time to cancel out Kieron Dyer's opening goal.
Much to the delight of the 20,165 crowd former United striker Lomana LuaLua was the creator as he turned his marker on the edge of the penalty area deep into first-half stoppage-time before centring for Stone to glance a low shot inside the right-hand upright.
Newcastle looked to be on their way to booking a place in the record books when they took the lead three minutes earlier after seizing on a mistake from Linvoy Primus.
The Pompey defender attempted to clear Lee Bowyer's deep cross from the right, only to head back towards his own goal for Dyer to pounce and bury a header from just four yards out.
Portsmouth had the better chances in the opening stages. Captain Arjan De Zeeuw should have done better in the tenth minute after Patrik Berger picked him out unmarked in the Newcastle penalty area, but he could only head over from eight yards.
Worse was to follow eight minutes later after LuaLua put strike partner Yakubu Ayegbeni in the clear following a mistake from Andy O'Brien, but the Nigerian ace dragged his effort well wide of goal.
Newcastle winger Laurent Robert was unlucky not to break the deadlock in the 37th minute when he powered a header against the underside of the crossbar and Portsmouth were able to clear to safety.
But Berger was a constant threat on the left and was only prevented from firing the home side in front by a brilliant full-length save from Shay Given. Berger let fly from fully 30 yards out and his effort was destined for corner before Given flung himself to his right to save.
Portsmouth goalkeeper Jamie Ashdown had to save smartly 11 minutes from time to keep out a crisp strike from Bowyer as Newcastle surged forward in search of their record.
The second half was littered with mistakes and missed passes and was more notable for the continuing flurry of yellow cards handed out by referee Matt Messias.
Messias had seen reason to caution five players in the first half and followed that by adding another four names to his notebook after the interval, much to the bemusement of Newcastle manager Graeme Souness and his Portsmouth counterpart Velimir Zajec.
Man of the Match: Lomana LuaLua
The DR Congo striker was a constant thorn in the side of his former team. LuaLua seemed determined to prove a point to the club that sold him in the summer and did so by creating Stone's equaliser.