Turn signal light stays on

Why does it do this? i'm probly just dumb, but it does it when my lights are on and just started. '91 xj, 4.0 HO, 4x4

If you mean the green indicator arrow on the dash stays lit, it's because one of your signals is not working. Check for burnt out bulbs. I'm not sure about other vehicles, but all chrysler products I've driven do this when a bulb blows.
Tony
For the record: '91 XJ 4.0 HO 4x4

It can also happen when one of the sockets doesn't have a good ground. Electricity seeks any ground path it can find, so if the designed ground path doesn't work, the parking light filament finds an alternate ground path by back-feeding through the turn signal filament, and that's connected to the dash indicator.

Ooo. So i have a smart jeep. That's kinda cool. Thanks for the help.