The Rules of Engagement

S4, E6: During an intimate moment, Nathan (Emmy Award-winning guest star Woody Harrelson, "Cheers") pops the question of marriage to Grace (Debra Messing) but she recoils simply because the situation didn't fit her childhood fantasy of a proposal - and when she realizes her mistake, she intends to return the favor and send out invitations. Meanwhile, Will (Eric McCormack) tries to soothe Grace's ruffled feathers while engaging ethically challenged Jack (Sean Hayes) and Karen (Megan Mullally) over the proper rules of bar-tipping.