Megson, who received the vote of confidence from the Forest directors after a defeat at Milton Keynes in midweek, was barracked by both sets of fans and saw his side go behind after just 14 minutes.
Marcus Bean, who passed a fitness test just two hours before kick-off, was the man who grabbed the goal by hitting an unstoppable 25-yard drive after being teed up by John Murphy.
Forest looked threatening from set pieces and Ian Breckin should have done much better with a free header after a cross from Nicky Southall.
Danny Cullip also got on the end of a Southall free-kick before Breckin made up for his earlier error by heading home a corner at the near post.
Blackpool restored their lead barely a minute after the break when a throw in by Marc Joseph was only half cleared and David Fox shot home from outside the area.
Things looked even bleaker for Forest on 66 minutes when defender Wes Morgan, who had picked up a yellow card in the first half, was sent off for a terrible tackle on Rory Prendergast which Premiership referee Dermot Gallagher deemed worthy of a second booking.
But Blackpool failed to make their numerical advantage tell and Forest pressed for an equaliser by throwing Cullip up front as an emergency striker.
The equaliser finally arrived with barely a minute of normal time left when defender Julian Bennett fired home from close range after another Southall free-kick caused havoc in the Blackpool penalty area.
His goal prompted wild celebrations among the 2,000 travelling fans as well as the players and management.