Continuity mistake: When Jay and Tee first start to talk to Jeff, Tee grabs the "weed." When Jeff gets mad and starts banging on the grate, the wide shot shows Tee in the same position, gripping Jeff's weed, however it was not digitally added in that shot, so he's gripping nothing. But in the next shot, he's shown gripping the weed again.
Character mistake: When Jeebs is showing them his deneuralizer and it shorts out a moment, he states he's still running off the 6.0. However the computer display shows he's using the beta 0.93.
Visible crew/equipment: When Jay is addressing the civilians in the small section of the subway car that is left after Jeff ate the rest, green screens are reflected in Will Smith's sunglasses before he neuralizes them.
Answer: They are extraterrestrials, the fact they are weird gives it away to K now he has been deneuralized. He started to notice them again as his mind is rebooting.
lionhead