Roger (Harry) Willis started his career at Grimsby, making just 1 league start plus another 8 appearances as a substitute before joining Barnet in 1990 for £10,000. Willis helped the Bees gain promotion to the football league by winning the GM Vauxhall Conference in 1991. He was part of the Barnet squad that made the Division Four play-offs in 1991/92, but left in October 1992 to join Watford for £175,000. He made 39 league starts plus another 5 appearances for the Bees as substitute and scored 13 goals.
Paul Warhurst joined Grimsby in March 2004 after being released by Carlisle. He made just 5 league starts and 2 appearances as a substitute for the Mariners before joining Blackpool. He joined Barnet in March 2006 and helped the Bees avoid relegation back to the Conference in 2005/06. He was released on a free transfer at the end of 2006/07. He made 18 league starts and another 10 appearances as a substitute for Barnet.
Des Hamilton is known at Underhill as the player who joined Barnet but never actually played for them. He joined the club as cover in 2004 from Grimsby when the Bees were chasing a place in the Nationwide Conference play-offs. He joined Grimsby Town in July 2003 and made 27 league appearances for the Mariners.
Michael Leary joined Grimsby in July 2009 from Barnet. He joined Barnet in 2007 from Luton Town and made 50 league appearances for the Bees, scoring 3 goals.
Dean Sinclair is currently in his second loan spell for Grimsby Town. Deano joined the Bees in the summer of 2004 after a successful trial period having been released by Norwich City. He played a big part in Barnet's Conference promotion season of 2004/05. He scored 19 goals in 125 league appearances for the Bees before moving to Charlton in 2007. He had a short loan spell at Underhill earlier this season, scoring in the home match against Crewe.