A graduate of the prestigious London Academy of Music and Dramatic Art (LAMDA), Gesner has appeared in several movies since his cinematic debut as "Dale's Man #1" in the 1994 comedy Dumb & Dumber, including Osmosis Jones (as Emergency Room Doctor #1), Me, Myself & Irene (Agent Peterson), Shallow Hal (Ralph), and There's Something About Mary (as a bartender).
Upon graduation, Gesner joined South Coast Repertory Theatre in Orange County, CA, performing in small roles and watching experienced actors ply their craft.
Towards the end of the course, he was offered a position in the general three-year programme at the Academy, whose North American alumni include such actors as Alexis Denisof, John Lithgow and Donald Sutherland.
Gesner made his feature film debut in Dumb & Dumber and put his real-life surfing skills to use as a surfer in the Chris Isaak music video, "Somebody's Crying".
Between shoots, Gesner added to his physical performance skills by picking up tricks from a local circus troupe, such as tightrope walking, inverted rope-climbing, kicking/flipping up from the ground (known as "kipping"), and stunt flips.
Gesner is brother-in-law to the Farrelly Brothers, and has received several small roles in their movies, including Dumb & Dumber, Fever Pitch, Kingpin, Me, Myself & Irene, Osmosis Jones, Shallow Hal and There's Something About Mary.