Lyndsy Marie Fonseca is an American actress. She began her career by appearing as Colleen Carlton on the CBS daytime soap opera The Young and the Restless, on which she starred between 2001 and 2005. Thereafter, she had a series of other recurring roles, including Penny Mosby on the CBS sitcom How I Met Your Mother, Donna on HBO's Big Love, and Dylan Mayfair on the fourth season of the ABC television series Desperate Housewives.