Who is Gil?
Currently the newest major addition to The Simpsons' cast of characters, Gil is one of many losers in Springfield, and has yet to hold a job for more than one episode. He is a parody of Jack Lemmon's character in the movie "Glengarry Glen Ross,"   which may explain why he looks similar to the character Frank Ormand in 4F08, who was voiced by Mr. Lemmon. Gil's voice is provided by Hank Azaria.

5F06 Working at Red Blazer Realty
5F10 Working as a salesman at Goody New Shoes
5F14 Awaiting an audit at the I.R.S. building
5F18 Working at a used car lot
AABF03 Installing computers at Springfield Elementary
AABF05 At the Leavelle's Bodyguard Academy
AABF06 Gambling his company payroll in Las Vegas
AABF10 Selling cars at the O.K. Car-Ral
AABF13 Salesman for Seņor Ding-Dong's Doorbell Fiesta
AABF19 Homer slaps him with a glove in the Kwik-E-Mart
AABF21 Telemarketing for the Springfield Shopper sales department
BABF03 In charge of "cleanup" at the Kwik-E-Mart
BABF14 Tries to sell Amway during an AA meeting

Thanks to the Simpsons Archive for this info.