Everton trailed at half-time thanks to a strike from Adam Johnson just before the break.
Fellaini brought Goodison Park to life late in the second half, scoring an equaliser before setting up Nikica Jelavic for the winner just two minutes later.
Hetinga took to Twitter to thank Fellaini for making the difference for David Moyes's men.
He tweeted: "Special thanks to Marouane Fellaini. With his goal and superb assist he was important again for Everton. Great teammate!"
A late win moves Everton up to fourth place in the Premier League as they continue to fight for a Champions League place.