Irma has often been shown to be eccentric, doing strange things such as dressing as a chicken, smacking a potato or even shaving her legs on the counter. A commonly run gag is her giving customers old, or inedible food, such as horseshoes in meals, or giving spilled coffee through a wet towel.
Irma has short black hair which is covered by a hair net. She wears glasses, a waiter uniform with a name badge, an apron and gray socks with blue shoes. In older strips, she has brown hair.
- In the strip from August 8, 1981 Jon is shown flirting with Irma.
- Odie has never met her.
- She is one of the few regular characters that have mainly appeared in the comic strip, although she did have cameo appearances in Garfield Caught In The Act (as part of the password section and the Whack-A-Character game).
- Jim Davis revealed that he borrowed Irma's name, but not her personality, from his aunt Irma.
- In the strip from May 26, 1985 she was shown with red hair.
- She runs the diner 24 hours a day with no help, though she does have chefs who cook the food.
- She has appeared 91 times as of the 1st of January 2017, the 19th most.
- She made a cameo on Jon Arbuckle's comic book in The Garfield Show episode, The Caped Avenger Rides Again!.
Irma usually doesn't serve food in an edible way, such as:
- There was a bird beak in a pie that Garfield ordered.
- She offered to give Jon a scoop of ice cream that dropped on the floor
- Her idea of "aged cheese" involves leaving it in her pickup for at least six months.
- She once gave Garfield and Jon a "Saturday Special" that was one week old.
- She gave Jon coffee by squeezing it out of a wet towel that she used to clean the coffee that another customer spilled.
- Her choices of coffee are regular and decaf.
- A meatloaf she once served had a horn on it.
- The chickens for the cooked chicken were diseased and coughing.
- She once accidentally served dog food to Jon.
- Serving Jon chicken soup that had feathers in it.
- Served Jon soup with a tooth in it.
- She once served Garfield and Jon cheeseburgers with 6 month old cheese.
- She once served Garfield and Jon cheeseburgers with one of her false eyelashes.
- She once, by mistake, put a horse shoe in Jon's meatloaf and Garfield's burger.
- Once the chef's cell phone was on Garfield's meal.
- The "chicken surprise" involves her putting on a chicken mask and saying "SURPRISE!"
- She once put water into Buttermilk pancakes and Buttermilk into the coffeemaker.
- Smacking a live fly in Jon's mashed potatoes.
- Taking dust from the floor and making a special called “dust bunny surprise“ from it.
- A "burger" is just a burger, a "deluxe burger" is a burger with a bun. Garfield assumes that the "super deluxe burger" comes with a plate.
- She uses the terms "soup" and "stew" interchangeably.
- Her "Pan-fried Ugly Fish" is served with the head, otherwise it would not be 'ugly'.