Welcome to the Greg Siff Fan Club!!! Contrary to popular belief Greg Siff and Seth Ullian are not the same person. This common misconception arises from the fact that they both starred in the popular Kevin Kline hit "In And Out".
The differences between Siff and Ullian---which are admittedly subtle---can be noted predominantly in their respective accomplishments. Siff has most recently put forth a stunning performance as Brandon in the summer smash hit "From Justin to Kelly"; he also played a character, whose name was not Seth Ullian, in "In and Out."
Seth Ullian, meanwhilst, does not star in "From Justin to Kelly." They both appeared alongside each other as "Locker Room Guy" in "In and Out." One key way in which Ullian and Siff differ is that Ullian played "Broker" opposite Ben Affleck (who, incidentally, is not the same person as Matt Damon) in "Boiler Room." Additionally, Ullian appeared as "Cute Waiter" in an episode of "Sex & the City." Some lament this casting, as Siff seems far cuter than Ullian; those who believe along these lines contend that Siff, not Ullian, would have been a better choice for the role. Lastly, Ullian (we think) was in the popular show "Stomp." While Siff's dancing skills landed him in his well know role in "From Justin To Kelly," he has NEVER danced on a garbage can and would NOT be reduced to filling such trival roles.
Greg Siff's superiority to Seth Ullian is proved once again in the fact that absolutely no where on the internet is there a picture of the inferior Ullian.