The staff are upset when Mr James doesn't invite them to his big Halloween party because they think they're too cool to dress up; Lisa volunteers Dave to wear "the most outrageous costume ever" to get them into the party spirit.
Did You Know?
To boost moral, Dave goes to the office Halloween party in Lisa ' s dress. This in reference to The Kids in the Hall, where Dave Foley would appear in skits as a woman as well as the rest of the cast. See more
During Dave and Matthew's brief exchange at the meeting table on the party and what Matthew went as, in one shot the pen holder on the table has three pencils, one facing left, and two facing right, then the shot cuts to Dave, then back to Matthew, and a third pencil has appeared on the right, though only Matthew has a pencil in that area and he's still holding it. See more
I might as well. After all, I am the belle of the ball.
More like party slut.
References The Kids in the Hall