The Toy

Jack Brown (Pryor) is a man in Baton Rouge, Louisiana in danger of having his house repossessed. After numerous unsuccessful attempts to get a job working for the local paper, the Bugle, he becomes so desperate that he ends up taking a job as a janitor for wealthy U.S. Bates (Gleason), who owns the paper and a department store among many other businesses. Brown is humiliated as he clumsily attempts to serve food at a luncheon while dressed in drag. He is fired from that gig by Bates, but "Master" Eric Bates (Schwartz), the spoiled-brat son of the boss, sees Jack while looking through Bates' department store. Amused at seeing Jack goof around in the store's toy section, Eric informs his father's right-hand man Sydney Morehouse (Beatty) that what he wants is Jack himself.
Morehouse fails to convince Eric that human beings cannot be owned. In exchange for a generous financial settlement, Jack agrees to be Eric's live-in friend during Eric's one-week spring break from military school.
Emotionally estranged from his father, Eric takes a liking to Jack but still manages to humiliate him with numerous pranks. After a particularly humiliating incident in the mansion incited by Bates' ditzy wife Fancy (Ganzel), who literally introduces him at a dinner party as Eric's new "toy," Jack grows tired of the situation and leaves. He agrees to return only when U.S. Bates (with Morehouse as his proxy) offers Jack so much money that he can not only stave off repossession, but retire the mortgage on his house.
Jack returns, determined to teach Eric how a friend is supposed to be treated. They bond while participating in mini-cart racing, video games, and even fishing in a stream filled with piranha. The pair decide to start a newspaper of their own for fun. After witnessing multiple examples of Bates' cruelty, they dig up dirt on him, such as a story of how he won his butler, Barkley (Wilfrid Hyde-White), in a game of billiards. They publish their paper and distribute it throughout the city. Bates is outraged.
To prove to his son that money can buy loyalty, he offers Jack a reporting job with his newspaper, which is what Jack wanted all along. When he accepts, Eric is upset because he thinks Jack is selling out. Jack tells Eric that most men (especially disenfranchised African-American men such as himself) need jobs, just as his priority is to support himself and his wife.
A swanky outdoor party is later held at the Bates estate. It is attended by wealthy businessmen and politicians, some of whom are unaware it is to be a fundraising event for the Ku Klux Klan. Jack's wife, Angela, (Annazette Chase) tries to bring attention to this through her watchdog group, but she leaves after Jack convinces her that he can get evidence of KKK involvement. When Jack learns the true reason for the party, to get the KKK Grand Wizard and a senator together in a picture, which would then be used by Bates to blackmail the senator into abandoning an indictment against him the senator was spearheading, he and Eric team up to thwart this. They both disrupt the party by driving go-karts all over the grounds and Jack embarrasses the Grand Wizard by causing him to fall into a bowl of chocolate pudding. Incensed, the Grand Wizard throws a pie at Jack, but hits a policeman instead, leading to his arrest for assault. After this, Bates chases after Jack in a golf cart but ends up crashing into the pool. Jack saves him from drowning, and it seems all is forgiven. Jack packs up and returns to his neighborhood with his wife.
The next day, while driving Eric to the airport to return to military school, Bates tries desperately to have a heart-to-heart talk. Eric runs off, making his way to Jack's house. Jack gently admonishes Eric to give his father a chance. Bates arrives then and confesses to his son how much he truly does love him and Eric finally accepts that as the truth as the two embrace. As he and Eric depart for the airport, Bates offers the newspaper job to Jack again and promises Eric that next year he can spend one week with him and one with Jack, much to Eric's joy.

Question: Who returned to teach Eric how a friend is supposed to be treated?
Answer: Jack