Passive Fish Springs to Life on River (HU)

[DoomSlice]

Villain in this hand is 63/3/.5 BEFORE we started to go to heads up. Mega-fish at the table just left and everyone dissapeared in one orbit except Villain and I. Villain loves to make "great" calls, once calling 3 pot sized bets on a JJ8QK board with T8 (beating the bettor's pocket 3s). This is the first time I've seen him take over the betting like this.

Hero is SB ($45) with J [img]/images/graemlins/heart.gif[/img]6 [img]/images/graemlins/heart.gif[/img]
Villain is BB ($40)

Pot Limit 25


Preflop:
Hero raises to .75, Villain calls .25

Flop ($1.5): J [img]/images/graemlins/spade.gif[/img]K [img]/images/graemlins/spade.gif[/img]4 [img]/images/graemlins/heart.gif[/img]
Villain checks, Hero bets $1, Villain calls

Turn ($3.5): 6 [img]/images/graemlins/diamond.gif[/img]
Villain checks, Hero bets $3.5, Villain calls

River ($10.5): 9 [img]/images/graemlins/club.gif[/img]
Villain bets $10.5, Hero????

Obviously QT comes to mind as a possibility, but he's been known to call down with ANY piece of the board, and I've been checkraised on the turn once when he had top pair weak kicker.