Eddie pursues Jessica into Toontown believing her to have just committed murder. Upon arrival, he notices a half-silhouette of a woman resembling Jessica doing her hair in a hotel window and proceeds to intercept. Once he gets there, the seemingly stunning woman immediately reveals herself to be an ugly woman named Lena Hyena, who instantly falls in love and chases after him upon sight. Not knowing where to turn, he retreats into the men's restroom.
Eddie discovers the restroom is non-existent leading to open air a million miles high in the sky causing him to plummet countless stories. Just as he's about to hit the street below, Lena manages to catch him just in time and gives him a big kiss very much to his dismay. The recoil of it was powerful enough to send him flying several yards down the street. Still madly passionate for him, she continues to run after him. He quickly tears a street line and places it towards a brick wall to which she mindlessly follows, flattening upon impact. She isn't seen again in the rest of the film.
Roger Rabbit's Toontown
Lena appears in the Roger Rabbit's Toontown issue, "The Kissing Bandit" where it's revealed she's actually been a long-time friend of Jessica. In the issue, Jessica visits Lena in Toontown as she's pursued by a Toon Wolf who's overly smitten by her. The Wolf keeps confusing Lena for Jessica in his multiple attempts to kiss her, much to his horror. He runs away not knowing what to learn from his shenanigans. Unaware Lena had a cold, the Wolf gets sick after kissing her so many times.
"Lena the Hyena"
Lena Hyena is highly similar to Lena the Hyena, a character created by cartoonist Al Capp for his comic strip Li'l Abner circa 1934. A resident of Lower Slobbovia, Lena was said to be the "ugliest woman ever", so much so that anyone who saw her went insane. Her face was always hidden often behind censor bars and word balloons or by being seen from the neck down. Capp later held a nationwide contest in 1946 to see who could draw the best interpretation of her. The winner was illustrator Basil Wolverton, who went on to do artwork for Mad Magazine.
There's been a long standing rumor that Roger Rabbit's Lena Hyena may have been loosely adapted from or was, at least, an obscure reference to the Li'l Abner character. While this all remains unconfirmed, it seems more than likely that they're just two completely different characters that happen to share a few traits.
Lena's scene was heavily inspired by a segment from the 1943 Tex Avery short Red Hot Riding Hood where Grandma chases the Wolf after he mistakes her for Red. It also references the moment when he runs through a door and almost falls off a very tall apartment building.
Real saliva was used when she kissed Eddie.
Lena in her brief Jessica guise
Lena in Roger Rabbit's Toontown: "The Kissing Bandit"