Hero is new to the game, probably has a tight image so far. MP is a somewhat taggish player maybe on the LAG side. UTG is a donk. CO is a loose, gambling type of player. He's unpredictable, sometimes passive, sometimes aggressive, will throw in a random limp-rr with crap and does weird stuff like that.
Hero is in SB with A
UTG limps, MP raises, CO calls, Hero 3-bets, all call.
Hero bets, UTG calls, MP calls, CO calls.
Check, check, check, check
Check, check, check, CO bets, Hero?