Believe it or not, actor Mario Lopez celebrates his 40th birthday on Oct. 10, 2013. Keep clicking to see more photos of the former "Saved by the Bell" star through the years. Here, Mark-Paul Gosselaar (Zack Morris, left), Tiffani Thiessen (Kelly Kapowski, left center), Lark Voorhies (Lisa Turtle, center), Elizabeth Berkley (Jessie Spano, right center) and Mario Lopez (A.C. Slater, right) star in "Saved by the Bell: Season Two."