Personally, I'm glad that Maggie Wheeler had such a hard time getting through takes with Matthew Perry, as Janice is probably my favorite Friends character besides the main six. In addition to the various tribulations that Chandler and Janice had during their relationship (remember when he flew to Yemen to break up with her?), she would also show up at the most inopportune moments in the main cast's life, like when Rachel was in labor and when Monica and Chandler were at the fertility clinic. Janice would suddenly appear and scream "Oh My God", sending the live audience into hysterics. But her appearances would also usually make the Friends realize something about themselves and move them forward, making her a fairly critical character in the show's overall narrative.