Pull up a barstool and make yourself comfortable — the cast of Cheers is finally reuniting! Well, at least two of the classic sitcom's co-stars are. In tonight's episode of ABC's 8 Simple Rules for Dating My Teenage Daughter (airing at 8 ET), barmaid Diane and mailman Cliff — aka Shelley Long and John Ratzenberger — drop in as the Hennessys' neighbors, Mary Ellen and Fred Doyle.

"Johnny was absolutely on his game, as he always is," an enthusiastic Long informs TV Guide Online. "This is a terrific character for him. Very different. And I got to do something new, too. There are bits and pieces of Mary Ellen that I don't think will be familiar to people who know my work. I'm also looking a little bit different, hopefully, than you've seen me before."

Unfortunately, although Long and Ratzenberger's Rules family lives next door to John Ritter and Katey Sagal's, there's little chance that the prime-time legends will reprise their roles anytime soon. "From the Hennessys' point of view, the door is closed," Long laughs. "From the Doyles' point of view, it's wide open. And therein lies the conflict, which is very fun."

Truth be told, the whole experience was a blast for the actress. "One day, we got some very funny new lines, which was a surprise because the original lines were quite funny," she explains. "And because they were so new, I still thought they were funny and broke up several times in rehearsal." Finally, she resorted to her own rules. "I had to tell [Ritter and Sagal], 'Okay, I can't look at you guys,'" she recalls, chuckling. "And they understood." Maybe next time, to make the former saloon mainstay feel more at home, craft services will stock up on beer and pretzels.