O'Neill was appointed Ireland boss last week to replace Giovanni Trapattoni and he has named former captain Roy Keane as his assistant.
Current LA Galaxy forward Keane has had loan spells at Celtic and Aston Villa, two clubs previously managed by O'Neill, but the pair's paths have never crossed before.
Keane is happy that O'Neill has taken on the Ireland job and he has been impressed by the Northern Irishman's initial impact.
"I didn't think I'd get this opportunity," said Keane ahead of Ireland's friendly with Latvia on Friday night.
"Despite all the speculation over the years I haven't had the pleasure of working with Martin before.
"It just never happened but now, thankfully, I will have and the last few days have just been very, very enjoyable."
O'Neill, former Manchester United midfielder Keane and ex-Ireland boss Mick McCarthy were the three names strongly linked with replacing Trapattoni, who left his role in September after Ireland's failed World Cup qualifying campaign.
And Ireland's record goalscorer Keane is delighted that two of the names in the frame will now be working in partnership.
He added: "The three names that were mentioned, I didn't think we would have two of them here.
"The news has given the whole nation a lift. It's been incredible and what everyone wanted.
"You don't get two bigger characters than Martin and Roy. Everything is enthusiastic about this partnership and the players are too."