Answer: Molly Shannon
Shannon landed the role of Betty Lou Who. Betty was Cindy Lou Who's mom and the wife of Lou Lou Who. In one scene, Betty was seen on her roof putting up Christmas lights and she mentioned that she wanted her house to look better than Martha May Whovier's home, which was next door. Martha came outside and said hello to Betty and Betty said hello back. Martha showed Betty a beautiful antique and Betty commented that it looked nice. Martha then unveiled a machine she had and used it to shoot up lights all over her house, which overwhelmed Betty. Midway through the movie, Cindy Lou Who told Betty and Lou that she wanted to do something nice for The Grinch and the town after he went on a rampage. Shannon guest starred on the TV series "Glee", "Pushing Daisies" and "30 Rock".