In the first team at 16, Sibbald played 35 games last season, while Fulton, son of former Celtic, Bolton, Hearts and Falkirk midfielder Stevie, turned 18 in April and has 40 first-team appearances already.
And while neither is believed to be Old Trafford material yet, it's a measure of Ferguson's thoroughness that he wanted a first-hand look at them on his own turf.
Bairns boss Stephen Pressley told the Sunday Mail: "They trained with the 18s on the Monday then, next day, they were playing with the reserves.
"They had guys like Anderson taking part and quite a number of the loan players who had been out in the Championship were back training in the side.
"It was a high standard but my lads acquitted themselves well. Their team won 2-1 and wee Sibbs scored both goals!
"It was a brilliant trip for them, so inspirational. Sir Alex spoke to them individually and as a pair. He was brilliant with both."