It starts out high, in short, piercing bursts. And it lingers, ever so briefly, until it dives, transforming from a lilting he-he-he to a full-on pig snort. The Steve Urkel laugh — the brilliance of which rests in the fact that it’s all performed in the nose — is as unmistakable as suspender-wearing, high-waisted Urkel himself. Family Matters, a staple of ABC’s TGIF Friday-night lineup, and the 1990s themselves wouldn’t have been the same without him. “Did I do that?” Urkel would have said. Yes, Steve, you did.