Dozens of forum and microblog users have uncovered that recent episodes of the popular Chinese television series Ipartment have many of the same plots, lines and jokes as well-known American TV series.

The posts have sparked heated discussion online because the show, now in its third season, started airing for a national audience last week on four major satellite TV channels across the country.

The group of online critics have accused producers of stealing ideas from shows such as How I Met Your Mother, Friends and The Big Bang Theory, according to posts on Sina Weibo, tianya.cn, the popular Chinese forum, and douban.com, an online community that focuses on books and movies.

Critics have posted screenshots with subtitles of different Ipartment episodes. Some offered links to edited video clips from previous seasons on youku.com, the online video website, to offer further evidence that the show's producers have long been copying ideas from American TV series.  

"Many lines and scenes have been completely ripped off from American shows. I thought it was shameful to do this. It is an insult to the American TV producers and an insult to the screenwriters and producers of original Chinese TV shows," said a netizen who asked to be identified by her English name Grace.

On Saturday, the show's producers sent an apology letter to a famous online joke and screenplay writer for using his jokes without permission. In the apology, the producers acknowledged that the show contained jokes from "various sources."

They offered to pay 10,000 yuan ($1,569) in compensation for every 1,000 Chinese characters of material.

One of the actors on Ipartment, Chen He, defended the show Friday in a report in the Shanghai Evening Post, saying the episodes were an homage to the American TV series.

However, Grace and other online critics didn't buy the explanation. Grace said that some of the 40-minute episodes are 30 minutes of plot copied from another show and 10 minutes of jokes compiled from other sources.

"According to Chinese copyright law, translating an original work requires that one first get permission from the author. Otherwise, it may result in copyright infringement," said Ren Haiyong, a Shanghai based lawyer specialized in intellectual property law.

Grace said she hopes her efforts will help promote originality on Chinese television.