When Lindsay Lohan and America Ferrera clash on the set of ABC’s show “Ugly Betty,” all bets are off. Pants as well, it appears.

It seems that even though “Mean Girls” star Li-Lo had signed with the TV network to appear on six of the comedy-drama series’ episodes, her agreement has been cut down to only four, since the actress has been constantly trying to steal Ferrera’s thunder on the set, in some sort of power play she fancied.

America Ferrera portrays lead character Betty Suarez in the series, an unattractive woman who wears braces, has bushy eyebrows and no sense of fashion, make-up and hair-style whatsoever. And she gives life to the ugly duckling quite well, since her performance earned her the 2007 Golden Globe for Best Performance by an Actress in a Television Series - Comedy or Musical, a prestigious award for which she outran Marcia Cross, Felicity Huffman, Julia Louis-Dreyfus and Mary-Louise Parker, who were her fellow nominees.

Nevertheless, Lindsay Lohan doesn’t seem to care about all that, given that a production source has revealed that during the shooting of the episodes, the actress smoked one cigarette after another, brought many friends who always managed to deface her dressing-room and also refused to begin filming unless America had arrived on the set, too.

Still, Ferrera found a way to get her revenge, as sources have stated that, while the two actresses were filming a scene from the episode entitled “Granny Pants,” the show’s star pulled down Lohan’s pants instead of going by the script and waiting for the latter to do that to her.

Oh, and it seems that Lindsay was not wearing any underwear at the time.

Bad day to go commando, Li-Lo!