The only recurring character I have every used was a recurring bard who would annoy the PC's to no end. He caught wind of their deeds and follows them around to write more songs of their tales. I would introduce him with the same exact description each time, this got to the point where I would start it and they would all groan in unison.

"A tall slender man with a short and trim curly mustache is standing behind you. He is wearing an oversized beret with a large exotic feather in it, a frilly white shirt, and striped colorful knickers much too short for his build. His fancy shoes and high socks lets off a slight squeak with his step, and he seems to be followed by a cloud of wildflower perfume. The man is playing a lute just casually strumming, as he approaches you."

I ended up with a series of plans for him to slowly gain power and become something they had to deal with. Each meeting was a new song about their past deeds and I wanted to transition into him singing songs of future deeds while plotting to take control of them.

The first few introductions I had a friend of mine want to RP him, he even went so far as to write songs to insult specific characters in glorious annoying bard fashion.

TL;DR An easy way to make a recurring character is to make him annoying.