Richard Feloni explains:

The Tumblr blog "Who is that hot ad girl?" is devoted to digging up the real identities of actresses in commercials. We noticed that many of the actresses' looks were toned down to sell products.

Common tactics include putting the actress in low-key makeup, baggy clothing, a relaxed hairstyle, and bland employee uniforms.

Below are some examples from Richard Feloni's post.

Fernanda Romero in her McDonald's commercial wears a big shirt over a swimsuit and messy hair to make the Mexican actress seem much more average-looking than she actually is:

Alisa Allapach is a friendly Best Buy clerk her holiday ad.

She's actually a former competitive ice skater who has appeared in movies like "The Hangover":

prefer the left

Nadine Heimann is an everyday dog lover in a Sergeant tick and flea repellent commercial:

Heimann is an actress/model who also starred in the popular Katy Perry and Timabaland music video: