Image Credit: NBCBetty White’s appearance on Saturday Night Live was truly golden: Last night’s edition posted its highest overnight ratings in 18 months. The telecast featuring White and musical guest Jay-Z averaged an 8.8 rating/21 share among 56 local markets tracked by Nielsen. That’s a high for the series since Nov. 1, 2008, when Ben Affleck hosted and Republican Presidential nominee John McCain appeared alongside Tina Fey as Gov. Sarah Palin.

In 25 markets with local people meters, last night’s edition averaged a 5.1/20 share among adults 18-49 – another high since the Nov. 1 telecast.

Not surprisingly, last night’s SNL was No. 1 for the night, topping all primetime programs on all major networks. In homes, SNL doubled the No. 1 telecast in primetime, which was ABC’s coverage of the NBA Playoffs (a 4.4/8 in metered markets). Versus the same night last year, SNL was up 66 percent in metered-market households. Besides White, last night’s edition also featured appearances by SNL alums Rachel Dratch, Fey, Ana Gasteyer, Amy Poehler, Maya Rudolph and Molly Shannon.

Final ratings, including viewer totals, for last night are due from Nielsen on Thursday.