England head coach Stuart Lancaster has frequently used special guests as a way of motivating or inspiring his squad, with Gary Neville and Bradley Wiggins among those to have addressed the players.
Strauss and Minichello were asked to give the squad an insight into handling high expectations and still delivering a top-class performance.
Ennis did exactly that during the Olympics, when she won heptathlon gold, while Strauss won two Ashes series as England captain.
"We're a pretty grounded group and no one is getting too far ahead of themselves," Lancaster said.
"Externally it's different. That's the reality of being an England team and that's the reality of the Six Nations. We've got to make sure we keep our eye on the ball and are not distracted by that.
"Our aim is to be a top-two side in the world by 2014 and if we want to be that side then we've got to be able to win games consistently.
"That's what we're striving for. We've not won every game but we haven't been smashed in any of them and we've always been competitive."
England's last game brought a magnificent 38-21 win over world champions New Zealand last month.
And Lancaster said: "The trick now is to build on that All Black performance and get the consistency we need to win at the highest level and (there is) no better place to prove yourself than the Six Nations."