Joel Barish
The protagonist of Eternal Sunshine of the Spotless Mind, played by Jim Carrey, is a cautious and somewhat reserved man. He lives with a "nice" woman named Naomi when he falls in love with erratic, bright-haired Clementine Kruscynski. They date for two years and have a bitter breakup, after which Clementine has Joel erased from her memory. Hurt and angry, Joel decides to do the same - but halfway through the process, he regrets it. Joel and Clementine care about each other deeply and have many regrets about the demise of their relationship.
Clementine Kruczynski
Joel Barish's love interest, played by Kate Winslet, is a spirited, exciting young woman who works at Barnes & Noble and frequently changes her hair color. However, beneath her passionate speeches and risk-taking behavior, she is deeply insecure. She impulsively has her memories of Joel erased after their bitter breakup, but later, realizes that something is wrong when her new boyfriend, Patrick, starts using Joel's memories to woo her. Winslet has often called Clementine one of the best roles she has ever played in her award-winning career.
Dr. Howard Mierzwiak
The pioneer of the memory erasing procedure and founder of Lacuna Inc, played by Tom Wilkinson. Dr. Mierzwiak is soft-spoken and serious, seeming to be the quintessential family man. However, his wife leaves him after she catches him with Mary Svevo, with whom he has had an affair in the past.
Mary Svevo
The receptionist at Lacuna, Inc is played by Kirsten Dunst. Mary's last name is a reference to Italian author Italo Svevo, who wrote Zeno's Conscience, a novel dealing with psychoanalysis and the revisitation of memories. Mary has a sexual relationship with Stan, but is infatuated with Dr. Mierzwiak. While drunk and high, Mary kisses Dr. Mierzwiak and finds out from his angry wife that she has already had an affair with Dr. Mierzwiak, but has had all her memories erased. Mary quits her job at Lacuna and returns all the files to Dr. Mierzwiak's patients.
Stan
A technician who works at Lacuna, Inc, played by Mark Ruffalo. Stan is a trusted employee and often performs the erasing procedure on his own. He has feelings for Mary Svevo and invites her over while he is deleting Joel's memory.
Patrick
A junior technician at Lacuna Inc, played by Elijah Wood. He falls in love with Clementine while he and Stan are erasing her memories of Joel. Afterwards, Patrick uses Joel's possessions to woo Clementine. He is desperate for her to like him, which eventually turns her off.
Frank
Played by Thomas Jay Ryan, Frank is Joel's nosy, single neighbor who only gets Valentines from his mother. He is jealous of Joel's relationship with Clementine.
Carrie
Joel's friend and Rob's wife, played by Jane Adams. She does not want to show Joel the card from Lacuna Inc that says Clementine has had her memory erased, because she is protective of his feelings. She and Rob fight constantly.
Rob
Carrie's husband and Joel's friend, played by David Cross. He is a pothead, and the one who tells Joel about Lacuna, Inc and Clementine's decision to have her memory erased.
Mrs. Mierzwiak
Dr. Mierzwiak's weary wife who leaves him after seeing him canoodling with Mary Svevo. Portrayed by Deirdre O'Connell.
