So says Harvey Keitel, as Mr Wolf, in Pulp Fiction, to a young female friend who only minutes earlier had helped him dispose of a dead body and bloodstained car in a scrap yard.
What is meant by this is that while a person may be funny, outgoing and fill a room with their presence upon entering it, they might also have next to nothing in terms of moral fibre.
And that brings us nicely, or not, to Jose Mourinho.
The Real Madrid manager remains eminently quotable, larger than life, is clearly an intelligent and talented football coach and is an interesting man - just not a particularly nice one.
At the end of Wednesday's second leg of the Spanish Super Cup, which saw Barcelona beat his Real side, Marcelo, the left-back, chopped down Cesc Fabregas with a brutal challenge.
A red card was forthcoming as was something of a mini-riot as those in white clashed with Barca players and staff on the sidelines.
Mourinho stood on the periphery, apparently refusing to get involved, when apropos nothing, he walked over to Barcelona's assistant manager, Tito Vilanova, and stabbed a finger in his eye from behind.
Vilanova, understandably, reacted with anger, but when he remonstrated with the Portuguese, Mourinho walked away with a smirk on his face.
Little is likely to be done in way of punishment. Mourinho and his club are way too big and powerful to ever really be taken to task by the Spanish Football Federation.
But Mourinho lost control this week at Camp Nou and surely lost every ounce of respect he had in world football.
He must know that nobody is listening to his complaints anymore. They are too busy looking up Lionel Messi's latest moments of genius on YouTube; the little Argentine conjured up two goals in Wednesday's 3-2 win for Barca, including a volleyed winner with three minutes to go.
At the moment, Barcelona are better than their old rivals, and there appears to be little Mourinho can do about it. He tried strong hand, defensive tactics last season, while in the past two matches Real took the game to Barca.
Defeat was the overall result on both occasions.
Real's points total in the past three seasons would have been comfortably enough to win the Primera Liga, if Barcelona had not earned even more.
Mourinho's men will likely always be second best as long as Messi, Xavi, Andres Iniesta et al are still about.
And Jose Mario dos Santos Felix Mourinho does not like being second best.
Is this why his behaviour is now just nasty?
Oh, sure it was amusing when he slid along the sodden turf on his knees at Camp Nou when his Chelsea team earned a Champions League draw with Barcelona a few years ago, but all he did then was ruin a good suit. Now his reputation is taking a hit, too.
Of this latest defeat, he said: "What I'm about to say is not a criticism, I'm just stating a fact: there were no ball boys in the second half, which is something typical of small teams when experiencing difficulties."
Yeah, it must be really difficult to be Barcelona and their remarkable manager, Pep Guardiola, right now. They must be the ones feeling small.
Mourinho was never an angel, but when you are in a powerful winning team, things often go your way.
Like the time in April 2005, when he reportedly snuck into a laundry bin to dodge a Uefa ban during Chelsea's quarter-final with Bayern Munich, which his team won 4-2.
It was alleged that Mourinho arrived early at Stamford Bridge for the game, viewed the match on television in the dressing room and proffered the pre-match and half-time talks. Ten minutes before the game finished, Mourinho is thought to have climbed into one of the laundry skips before being wheeled away to the ground's nearby leisure club where he spent the night.
Oh, how we giggled.
Then he called Arsene Wenger a "voyeur" and suggested the Arsenal manager was obsessed by Chelsea to the point that he could not stop staring at them.
It was hard not to at least chuckle.
These days, few find anything Mourinho does remotely amusing.
Mourinho has the most expensive squad of runners-up in history, and this has clearly affected his judgement.
Questioned on the incident with Vilanova, he said that he didn't know who "Pito" was, a deliberate mispronunciation of Tito. "Pito", incidentally, means a part of the male anatomy in Spanish.
Mourinho also claimed that he has never known the identity of Barcelona's assistant coach. For a man famous for having 40-page dossiers on every opponent, this is difficult to believe.
Whenever the Special One is depicted in cartoon form on the back page of the Barcelona newspaper Sport, he is always wearing a straitjacket. How apt.
Mourinho is no longer a character, rather, he is a poor caricature.