<Directly after they are transported into the past, in the first scene where Worf appears>
Kira: Worf! What happened to you?
Worf: I 'm not certain, but I guess that when the chroniton surge washed over us and we were temporally displaced, there must have been some quantrumchronodynamic tachyon interference with my DNA and .... nah, just F it. This is getting too ridiculous, even for Star Trek. They changed my makeup, so that I look like the Klingons of this era, even though they are now supposed to always have looked like I still did fifteen minutes ago!