The stockbroker is a man who was telling Homer about his stocks as Homer was unaware that he has some.
History
Homer never sees the stockbroker, but he called Homer and gave him the news that his stock in the power plant went up for the first time in ten years. Carried away, Homer sold the stock for 25 dollars and missed the huge rise in share price on the news of the sale of the power plant that could have earned him $5200. Unlike Homer, apparently due to his dumbness, because he had bought his shares for 25 cents, all the other employees had bought them for 100 dollars.
Appearances
Episode – "Burns Verkaufen der Kraftwerk"
Episode – "Marge vs. the Monorail" (seen at town meeting)
Episode – "The Twisted World of Marge Simpson" (cameo)
Episode – "Realty Bites" (at police sale)
Episode – "When You Dish Upon a Star" (at court)
Episode – "Pray Anything" (cameo)
– The Simpsons Movie