Last night the episode where George found a dog and ended up keeping him aired. But Lucky was never seen or mentioned again.

As I recall he did make one or two more appearances. But yeah, apparently they forgot about him. This was the second season when the producers were experimenting with new directions to go into. By the end of the season Dick would have his TV show and the format would be finalized.

The dog was probably a lot of trouble to take care of, train, etc. and didn't bring much to the show, so they moved away from that idea. Though the scenes with Kirk and the dog were pretty hilarious I have to say.

They were! The dog sure sensed an evil character, lol

And George tells Steph "If your ever feeling down, your always welcome to come up to my room to get Lucky" (paraphrase) LOL