Defender was Williams Electronics' first video game; they had previously produced only pinball machines. The sound effects in Defender came from the company's earlier pinball games, most notably Firepower.
The NES adaptation of Defender II borrowed a few sounds and songs from Punch-Out!!. The title screen tune of Defender II is the "begin round" music from Punch-Out, albeit with a Star Wars-esque flourish at the end. The tune that plays when you win a round in Defender II is the music that plays when you lose a match in Punch-Out. Lastly, and much more subtly, the sound of enemies exploding in Defender II is one of the sound effects that plays when an opponent in Punch-Out is knocked down.
The arcade game was featured in the music video "Almost Over You" by Sheena Easton. At the bridge of the song, Sheena drops the machine over the balcony. Even in The '80s, never ditch your girlfriend over video games.