S4, E1: Will (Eric McCormack) returns from vacation to discover that Grace's (Debra Messing) romantic relationship with neighbor Nathan (Emmy-winning guest star Woody Harrelson, "Cheers") is humming along - but Nathan feels neglected when Will and Grace resume their chummy friendship, complete with their own private language and code. Meanwhile, Jack (Sean Hayes) proudly takes his newfound son (Michael Angarano) shopping for school at Barney's while Rosario (Shelley Morrison) and Karen (Megan Mullally) each cruise the merchandise looking for the perfect "anniversary gift."