Eileen is the love interest of Rigby on Regular Show. Although Rigby didn't have feelings for her in the beginning, he warms up to her because of her kindness and helpuflness that she and Margaret provide for him and Mordecai. She is a humanoid mole (though she looks like a human) with brown hair, glasses, and she wears a pink shirt, and a purple skirt; she's voiced by Minty Lewis.
Eileen appears in the show as a waitress along with Mordeacis love interest MArgaret. Eileen has a crush on Rigby, but he didn't love her at first till later on in the series where he enjoys her company and becomes her boyfriend. He goes to her if he needed any assistance or help. She was born in 1986. She first appeared in the episode "Brain Eraser". She also appears in "Do Me a Solid", where Rigby learns of Eileen's crush on him (even though Rigby shows no interest in Eileen), though he goes along with it for a while. Since the episode "Camping Can Be Cool", Rigby has warmed up to Eileen and considers her a cool person and praised her actions throughout the episode. In the episode "Diary", Rigby admits that he finds Eileen to be attractive without her glasses on. In the episode "One Pull Up", Eileen helps Rigby train for his company physical and he shows his gratitude by hugging her (and crushing her due to his enlarged physique).
In "MCF: The Song of Circe", she is visiting and happens to hear about the MCF's adventures from the girls' employees.
- In "Camping Can Be Cool" it is revealed that she's good at camping because of a phase she was going through, where she got lost in the woods a lot.
- She is allergic to duck dander.
- Eileen always walks barefoot.
- In "Brain Eraser" her glasses were clear inside and she had black frames but afterwards, the insides were changed to white and she the black frames were replaced with red ones.
- "Access Denied" is the only time (besides First Day) that Eileen wears her hair differently; completely down without the side ponytail, slightly wavy
- Before Margaret left for Milton University, "One Pull Up" was the first and only episode that you saw Eileen present and she is not accompanied by Margaret
- In "TGI Tuesday" she is seen dancing in both "free style" and ballet.
- In "Tants" it is shown that she can sew pretty well as she helps make Mordecai and Rigby replacement pairs of tants. It is also mention in"New Year's Kiss" when Rigby asks her what her New Year's Resolution is when she states "...I'd like to work on my craft log more..."
- In 'MCF: The Song of Circe", it's revealed that she wouldn't take the news of Rigby with another woman easily.
- MCF: The Song of Circe(Debut)