Not knowing your specific car, I'd say the bulb out monitor is applying power to the bulb looking for continuity. If not this, perhaps the cruise control bleeding back or a trailer light adapter bleeding ( that converts a Euro 3 filament to US 2 filament )

Does this only occur when the parking lights are on? If so, you have a poor ground for the rear lights.

As for the alternator waking up, this occurs on some cars in general when the idle speed to too low, alternator warning light can't pass enough current / is missing.