The WB’s launch of its midseason comedy “Smart Guy” scored the netlet’s highest overnight ratings ever for a premiere with a 6.4 rating and 10 share, according to Nielsen.“Smart Guy” was the No. 1 show in its Wednesday 8:30 slot in New York with a 10.7/15 and was second-rated in Los Angeles at 9.2/13. It was also No. 1 in Atlanta and New Orleans. Fox’s season finale of “Party of Five” posted its second-best metered market performance with a 10.4/16 and was up 15% over its “Beverly Hills, 90210″ lead-in.