Green’s Dictionary of Slang

1. (drugs) a crack cocaine addict [clings on to every morsel of crack].

2001

ONDCP Street Terms 13: Klingons — Crack addicts.

2. a piece of excrement clinging on to the anal hairs.

1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: kling-ons n. 1. Winnits; dangleberries; anal hangers-on. 2. One of many Star Trek aliens with bumpy foreheads.
2001		OnLine Dict. of Playground Sl. 🌐 klingon n. 1) Piece of excrement that sticks stubbornly to the buttock and/or buttock hairs.

3. a tedious or unpleasant person.

1997		Eble Campus Sl. Apr. 5: klingon – person who habitually displays affection toward another in public.
2001		OnLine Dict. of Playground Sl. 🌐 klingon n. [...] 2) an excessively stupid or unpleasant person.