It's a well known fact that characters described as homely or even ugly in their books usually become vastly more attractive in the TV adaptation (exhibit A the way Hermione Granger's famous bushy hair gradually metamorphosed into artfully tousled curls between movies). While Tyrion in the books is described as hideous and misshapen as well as being of limited stature, he is portrayed on TV by the rather handsome Peter Dinklage.
Tyrion's appearance was set to take a turn for the worse in the episode Blackwater when a large chunk of his nose is cut off during an attempt to assassinate him on the battlefield, leaving him looking not unlike Lord Voldermort. In the series this "disfiguring" injury was reduced to a scar that was more rakish than anything else and was described by Margaery Tyrell as making him more attractive.
This probably wasn't a bad decision when you consider the extra time spent on makeup and the fact that TV is a visual medium and TV audiences by and large expect at least moderately attractive actors to look at. Peter Dinklage's natural charisma, charm and good looks have turned a character traditionally loved for his quick tongue and clever mind into one who many consider a sex symbol.
I can't help feeling that Tyrion, the self proclaimed "god of !*$% and wine" would approve.