I think that would be Captain Crook! Here are the characters, thanks to Wikipedia:
Characters
Ronald McDonald - The primary icon of McDonald's characters.
Sundae - Ronald's dog. He only appears in "The Wacky Adventures of Ronald McDonald." Sundae was portrayed by Verne Troyer and voiced by Dee Bradley Baker.
Grimace - Grimace is an anthropomorphic purple tastebud.[citation needed] Initially, Grimace was the "Evil Grimace", with two pairs of arms with which to steal milkshakes. After that first campaign, the character was revised to be one of the "good guys", and his number of arms was reduced by two. Commercials and merchandise generally portrayed him as a well-meaning simpleton, whose clumsy antics provided a comic foil to Ronald McDonald. The character was retained after the streamlining of the characters in the '80s. His Uncle O'Grimacey [see below] would visit only one month per year, bringing Shamrock Shakes. Additional family were revealed in a McDonaldland VHS tape "The Legend of Grimace Island": He has an unnamed mom, an unnamed dad, a grandma named "Winky", a great, great grandma named Jenny Grimace, and a possible ancestor named "King Gonga". King Gonga is the king of all Grimaces. In "Grimace's Oddysey", Grimace has the hobby of ham radio and often sends out transmissions through a homemade transmitter made from a colander. Ronald says Grimace has his mother's eyes, Birdie says he has his father's prominent chin, and Hamburglar jokingly says he has his Grandma Winky's fat ankles. Grimace said he's proud of them. Grimace was voiced by Frank Welker in the commercials and by Kevin Michael Richardson in "The Wacky Adventures of Ronald McDonald."
Hamburglar - The Hamburglar was a thief who was dressed in a black-and-white hooped shirt and pants, a red cape, a wide-brimmed hat, and red gloves whose primary object of theft was hamburgers. The Hamburglar's early dialogue was a continual muttering of "BURGER, BURGER, BURGER" and gibberish with Captain Crook occasionally translating for him. His catchphrase was "Robble, Robble." Later dialogue included normal words in a child-like voice. Hamburglar was later retired. In the 2000s, he was temporarily revived for an ad campaign for generic burgers instead of Happy Meals. He was originally voiced by Howard Morris (who also directed many of the TV spots), Charlie Adler in some 80's commericals and "The Adventures of Ronald McDonald," and Carl W Wolfe in some 90's commercials[2]
Birdie the Early Bird - She was the first identifiably female character, introduced in 1980 to promote the company's new breakfast items. She is a yellow bird wearing a pink jumpsuit and flight cap and scarf. In the ads she is frequently portrayed as a poor flyer, and somewhat clumsy in general. Birdie's origin is explained in one old commercial: a giant egg falls from the night sky into McDonaldland, and Ronald McDonald decides to show the egg love. When the egg hatches, Birdie was so happy that she had already made friends that she decided to stay in McDonaldland. Birdie was voiced by Russi Taylor in the commercials and by Christine Cavanaugh in "The Wacky Adventures of Ronald McDonald."
Fry Kids - They are characters used to promote McDonald's french fries. When they first appeared, they were called Gobblins and liked to steal and gobble up the other characters' french fries. Accompanying them was the "Keep Your Eyes on Your Fries" jingle. Their name was later changed to the Fry Guys, then the Fry Kids, as female characters (the "Fry Girls") were introduced. They are differently-colored, shaggy, ball-like creatures with long legs and no arms, almost resembling a pom-pon with legs and eyes. Most of the time they are mute, but when they speak they talk in some sort of gibberish. In other commercials, they all talk very quickly at once. Their only facial features are bulbous eyes and thick, black eyebrows. The characters were retained after the streamlining of the characters in the '80s. The Fry Kids were voiced by Kath Soucie, Paul Greenberg, and Nika Futterman in "The Wacky Adventures of Ronald McDonald"
Mayor McCheese - Mayor McCheese has an enormous cheeseburger for a head, and sports a top hat, a diplomat's sash, and a pair of pince-nez spectacles. He is portrayed as a giggly, bumbling, somewhat incompetent mayor. He was based on H.R. Pufnstuf. Though the character was dropped during the streamlining of the characters in the 1980s, he did appear in a 1999 "The Wacky World of Ronald McDonald" VHS entitled "Have Time, Will Travel". Mayor McCheese was voiced by Howard Morris impersonating Ed Wynn in the commercials and by Bob Joles in "The Wacky Adventures of Ronald McDonald."
Officer Big Mac climb-in jail playground.Officer Big Mac - In addition to McDonald's signature sandwich, Big Mac was the name of a character in McDonaldland. He was similar to Mayor McCheese in that he had a large Big Mac for a head, except he was the chief of police and as such he wore a constable uniform with a disproportionately small custodian helmet resting atop his head bun. As the main source of law and order in McDonaldland, Big Mac spent most of his time chasing the Hamburglar and Captain Crook. He was featured in several of the campaign's commercials throughout the late '70s and early '80s. The character was dropped during the streamlining of the characters in the '80s.
Captain Crook - Captain Crook was a pirate and is similar in appearance to the famed Captain Hook from Disney's 1953 movie Peter Pan. Unlike the Hamburglar, this villain spent his time trying to steal Filet-O-Fish sandwiches from citizens of McDonaldland while avoiding being caught by Officer Big Mac. He would often translate for Hamburglar. As part of the nautical theme of the character, Captain Crook used ships and waterways as means to escape being captured. In his final appearances, he was renamed simply "The Captain" and his character design made less sinister. The character was dropped during the streamlining of the characters in the '80s. Captain Crook was voiced by Lennie Weinrib.
The Professor - A mad scientist-type character in a lab coat. He was introduced in 1971. The character was dropped during the streamlining of the characters in the '80s. The Professor was voiced by Howard Morris in the 70's and by Andre Stojka in the 80's.
The Hamburger Patch - The Hamburger Patch is part of the fictional city of McDonaldland where McDonald's hamburgers "grew" like fruit on plants from the Hamburger Patch. Even though hamburgers in McDonaldland were anthropomorphized and spoke, they were picked by characters such as Ronald McDonald and the Hamburglar for consumption. Advertisements featuring the Hamburger Patch were shown as evidence during the McLibel court case in the United Kingdom. During questioning by defendants, McDonald's Senior Vice President of Marketing David Green admitted that showing the reality of meat production "would not be very appetizing". The Hamburger Patch also featured in books and toys used to promote McDonald's. The characters were dropped during the streamlining of the characters in the '80s.
Iam Hungry - A short-lived McDonaldland character who was the self-proclaimed "Vice President of Snacking." He was introduced in 1998 and dropped in the early 2000s. The character was a floating, fast-moving green fuzzball with orange arms and a monstrous face. He would often appear when Ronald was dining with kids and would constantly crave food. He would never leave them alone until he got fed. Iam Hungry was featured in "The Wacky Adventures of Ronald McDonald" VHS titled "Visitors from Outer Space." Iam Hungry was voiced by Jeff Lupetin.
CosMc - A temporary character from McDonaldland. He was featured in a series of McDonald's commercials in 1990 when the McDonaldland gang went to the moon. CosMc was an alien who wore a large space suit, and he talked like a surfer dude. CosMc was featured as a character in the video game M.C. Kids. CosMc is voiced by Frank Welker.
Griddler - A short-lived McDonaldland character. He was featured in 2 commercials in 2003 to promote the McGriddles by stealing them from Ronald and his friends.
The Happy Meal Gang - A Cheeseburger, soft drink, and fries in regular size that were introduced in the 80s. They were later joined by the McNugget Buddies. The Happy Meal Drink was voiced by Hal Smith and the Happy Meal Fries was voiced by Bob Bergen.
The McNugget Buddies - A bunch of chicken nuggets in regular size. They were introduced in the 80s. The McNugget Buddies were voiced by Hal Rayle in the commercials and by Pamela Adlon, Lisa Raggio, and Charlie Adler in "The Wacky Adventures of Ronald McDonald."
Uncle O'Grimacey - He was created for an advertising narrative of the McDonald's fast food restaurant chain both in celebration of Saint Patrick's Day and to mark the annual appearance of the Shamrock Shake. O'Grimacey is the Irish uncle of the character Grimace and is a variant of the Grimace-design in that he is green instead of purple, sports a frock coat covered with several four-leaf clovers, and carries a shillelagh. His design motif is not unlike that of a stereotypical depiction of the Irish folkloric leprechaun, similar to the mascot of the football team for University of Notre Dame. O'Grimacey resides in his home country for eleven months of the year and visits his nephew Grimace in March, bringing with him his "incredibly delicious" shake. Uncle O'Grimacey is no longer used by the chain for its promotions of the shake.
Mike the Microphone - He was a one-time character created for the Kid Rhino album Ronald McDonald presents Silly Sing Along. He guards the door and runs things inside the McDonaldland Magical Radio Station, which Ronald and some kids use for their "Silly Day Broadcast". Mike was voiced by Larry Moran.
McDonald's had little Beanie Babies in their Happy Meals over the summer - they had something like 50 different Beanies - one of them was Grimace. The kids had no idea what he was! 
Thanks for a good laugh Tracy!
I know, scary!
