So you have your O1 visa approved and stamped in your passport. You hit the ground running in La La Land and boom, a big Studio wants to hire you for an episode of one the most watched shows in the US. You consider this your first big US break and if it goes well, your US career will also take off.
Then the legal department for the Studio wants to review a copy of your O1 Visa to make sure you are able to actually work for them. The copy of your O-1 Visa should include: A copy of the immigration forms, the sponsor letter, the agreement between you and your representative, an itinerary and the advisory opinion letters. But this NEW production is not listed on your Itinerary as one of the proposed projects you are coming to perform. What now?
Hopefully, you have an O-1B “Representative” Visa as an Actor. That means that your O-1B Agent/Manager is representing you before USCIS and the entertainment world for the purpose of you coming to the US to work with different productions.
Under the consent and representation of your O-1B Agent you may add additional engagements without filing an amended O-1B petition.
The section of the law that addresses this issue is 8 C.F.R. 214.2(o)(2)(iv)(D). Which states:
Amended petition. The petitioner shall file an amended petition on Form I–129, with fee, to reflect any material changes in the terms and conditions of employment or the beneficiary’s eligibility as specified in the original approved petition. In the case of a petition filed for an artist or entertainer, a petitioner may add additional performances or engagements during the validity period of the petition without filing an amended petition, provided the additional performances or engagements require an alien of O–1 caliber.
Since this is an O-1B Artist/entertainer situation, the O-1B Agent may add additional performances or engagements during the course of valid O-1B visa status without filing an amended petition. This will obviously save a tremendous amount of time, money and grief.
What does the Agent have to do to add an engagement or production? It can be as simple as providing the Studio 
with a letter stating that the Agent is adding this “big time” role as an additional engagement without having to file an amended O-1B petition.
So you have made it “big time” and are now on your way! Make sure to receive the proper advice about the type of visa to obtain and the proper classification, if not your “big time” will be “small time”.
As always do not hesitate to contact a qualified US Immigration Attorney with years of experience obtaining O1 Visas.