Sons Of Mogh featured the return of Kurn, the brother of Worf, in his only appearance in Star Trek: Deep Space Nine. Kurn had a bit of a character arc alongside Worf in his Star Trek: The Next Generation appearances, and frankly it is always good to see Tony Todd on screen. Just take a look at his other appearance in DS9 as an older Jake Sisko in The Visitor if you want a look at what Todd can do. This episode was a proper crossover, but wasn't much of a surprise as since Worf joined the crew of DS9 it was just a matter of time before his brother showed up. Although Kurn appearing was initially pleasing, it just seems very out of character to find that he wanted to die because of the dishonor to his house something he had dealt with before. Kurn ends the episode with his mind wiped and his face changed, and with no idea left that he is Worf's brother. It still would have been fairly easy to revisit the character in later episodes despite the memory loss, but it was a plot point that was left open which the writers never returned to.