Nah, ghosts are all see-through and they can't touch anythin'! You're not like that.

[She can punch things. Goku walks quickly through the crowds, looking at the stalls and getting distracted by anything shiny while still rushing along- then he suddenly stops and backtracks a few steps.]

Oh, look- I mean, don't! [He puts his hands on Nia's shoulders and spins her around so she's facing the other direction.] Wait here a sec.