Non-sense!!! Yes you are right; we are talking about Dilip Joshi aka Jethalal of Tarak Mehta Ka Ooltah Chasma who scolds his on screen wife Daya (Disha Wakhani) for every silly mistake. But not many people know that he actually gets a very respectful title from her in reality.
Our source from production informs, "Most of the team member along with Disha Wakhani, his onscreen wife entitled him by saying "Sir"."
Dilip Joshi is veteran to them and is also known for his humour very well. Though Disha may be his onscreen wife but just to respect him and his seniority, the whole cast call him by that kithab.
Our source informs that, "Recently while giving an interview to the news channel, she requested the reported that if she could let Dilip Sir joins her for that particular interview. The reporter was shocked to see Disha calling him sir and thus immediately asked the reason for giving him this kithab."
source : http://www.tellycafe.sampurn.com