Well, they weren't singin' and it wasn't rainin', but the stars of Singin' in the Rain couldn't resist giving Melbourne city dwellers a look at their dance skills.     An impromptu tap performance was on the cards when The Eye took actors (from left) Todd McKenney, Rachael Beck and Wayne Scott Kermond to the street for a photo.     The three were just as energetic on Friday during the opening night performance of the musical, which included a spectacular rain scene with the trio pelted with sheets of water.     With eight performances a week, we'd hate to be paying the Regent Theatre's water bill.     Getting a straight answer from the constantly joking and fast-talking threesome proved to be just as difficult as we imagined dancing on the slippery stage must be.     For example:     Have you all been tap dancing for a long time?     "Well, I had to teach Rachael," McKenney joked.     Kermond continued, laughing: "That's why she doesn't tap very well."     And Beck finished, "Yes, Todd taught me all the bad bits."     The petite blonde, who is probably best known for her role on the television sitcom Hey Dad, said she did not mind that people remembered her for her time on the '90s show.     "They were some of the best years of my life -- I had so much fun doing the show and I am so proud of it," she said.     "I was shopping the other day and there were some Japanese girls in the store and they said, 'Rachael Beck from Hey Dad, we watched you every day, you taught us English.'     "To tell you the truth, I'm quite flattered because that was nine years ago, so I mustn't have changed too much.  I hope they're still yelling it out in another nine years."