Parenthood

Gil Buckman (Steve Martin) is an anxious sales executive in the St. Louis area. When he finds out that his eldest son, Kevin (Jasen Fisher), has emotional problems and needs therapy, and that his other two children, Taylor (Alisan Porter) and Justin, may have issues as well, he begins to blame himself and questions his abilities as a father. When Gil's wife, Karen (Mary Steenburgen), announces she is pregnant with their fourth child on the same day he quit his sales job, he is unsure whether he can cope.
Gil is also concerned and convinced that the financial burdens of another child and office politics at work are turning him into the distant workaholic he hated his own father, Frank (Jason Robards), for being. Stressed by family and work issues, he opens up to Frank about his doubts as a parent. Frank tells him that he worries too much, and they have a reconciliation of sorts with Frank telling Gil, that fear and apprehension for one's children never ends. When a hired cowboy character fails to show up at Kevin's birthday party, Gil dresses up as a cowboy himself and hilariously understudies the role.
Gil's sister, Helen (Dianne Wiest), is a divorced bank manager whose dentist ex-husband wants nothing to do with their kids, Garry (Joaquin Phoenix) and Julie (Martha Plimpton).
Garry, who has just entered puberty, is shy, friendless, and likes to be alone in his room with a mysterious paper bag. At first Helen worries that it contains drugs or alcohol, but it actually contains porn videos and Playboy magazines.
Julie is still in high school. In spite of her high SAT scores, she is not interested in her education. She and her slacker boyfriend, Tod Higgins (Keanu Reeves), get married, ultimately resulting in her becoming pregnant and him moving into Helen's house. When Helen asks Tod to talk with Garry, he is able to reassure Garry that his obsession with girls and sex is normal for a boy his age, something that is a relief to Garry. This also increases Helen's respect for Tod. Eventually she supports his and Julie's relationship to the extent that when Julie wants to break up with him, Helen orders her to face her fears and to support him. She also begins to date Garry's biology teacher.
Gil's other sister, Susan (Harley Jane Kozak), is a middle school teacher married to Nathan Huffner (Rick Moranis), an intelligent scientist. They have a precocious daughter, Patty (Ivyann Schwan). Susan wants more children, but he is more interested in Patty's cognitive development. Patty, while intelligent, has difficulty relating to other children. Susan lashes out by compromising her diaphragm as a plan to get pregnant against Nathan's wishes. She eventually gets so impatient that she leaves him. He eventually comes to one of her classes and serenades her to win her back, promising her he will try to change. She agrees to move back home.
Larry (Tom Hulce), Gil's brother, is the black sheep of the family, but is Frank's favorite. Rather than settle into a career, he has drifted through life trying to cash in on get-rich-quick schemes. He has recently shown up, along with his son, Cool (Alex Burrall), who was the result of a brief affair with a Las Vegas showgirl, and asks to borrow money from Frank. It soon becomes apparent that he needs it to pay off his gambling debts, or else he must pay with his life. Frank is disappointed, but still loves him and tries to help. Frank refuses to bail Larry out completely, but offers to teach him the family business so he can take over for Frank (who offers to put off retirement) and use the income to pay off the debt. Larry instead deserts his son and leaves for Chile never to return, and Frank agrees to look after Cool.
The family is reunited at the hospital when Helen gives birth to a girl. Frank embraces Cool. Tod and Julie are together, raising their son. Susan is visibly pregnant. Gil and Karen are now the parents of four, and his boss has rehired him.

Question: A hired cowboy character failed to show up where?
Answer: At Kevin's birthday party.