Possible to Train in One Branch in ROTC, then Serve in Another?

Pure hypothetical as my DS has his dream path in his hand... (go ahead and sing it with me - He's got the whole...world... in his hand...)

Just out of curiosity, is it possible to train to become an officer / commission from 4 years in one branch's ROTC, then actually serve in another? U know it would be exceedingly rare, but is it ever done?

Ex. AFROTC to NAVY
Ex.2 - NROTC to AIR FORCE

While at the academies, apparently there is some cross pollenation where a handful of cadets from West Point and Annapolis switch academies, and live for a semester at the other. I'm assuming the same happens at the Air Force academy. There also reportedly is some history of West Point grads serving in the Navy, and visa-versa. Again rare but done (reportedly). Is it ever done from ROTC to service?

I recall there was a similar thread (I did not find it) in which the idea was if I recall was strongly dismissed because the ROTC branch paying for the education wouldn't appreciate the soldier/officer taking that training elsewhere, but wish to ask - ultimately, is it possible?

There are a few (and I mean few) ROTC/SA grads that cross-commission each year. My CO at my unit actually was an Air Force Academy Grad, but was set that he didn't want to fly or be in an office (not saying that Air Force is non-combatant), so he went to a recruiter that said he would be perfect to go to this "camp." Was sent out the next week, and spent 6 weeks at this "camp," in which he then became a U.S. Marine Corps Officer. He has enjoyed the infantry for 27 years ever since.

back in the day at Citadel occasionally a guy would move from one ROTC to another - usually it was to Army ROTC

I'm a West Point guy, but no other commissioning source offers a person more career options than the U.S. Merchant Marine Academy. You can choose to be a ship's officer at sea, ashore in the maritime and intermodal transportation field, or as an active duty officer in one of the Armed Forces. https://www.usmma.edu/after-graduation

Robert Kirkland, LTC (Ret)
"The Insider's Guide to the Army [and Air Force] ROTC Scholarship for High School Students and their Parents" (Amazon)

AROTCPMS said:

I'm a West Point guy, but no other commissioning source offers a person more career options than the U.S. Merchant Marine Academy. You can choose to be a ship's officer at sea, ashore in the maritime and intermodal transportation field, or as an active duty officer in one of the Armed Forces. https://www.usmma.edu/after-graduation

Robert Kirkland, LTC (Ret)
"The Insider's Guide to the Army [and Air Force] ROTC Scholarship for High School Students and their Parents" (Amazon)

Click to expand...

I’ll second. I know a guy on active duty in the Air Force who commissioned out of USMMA. Not exactly sure how he was qualified to be an Air Force officer but they took him anyway.

+1. DS is Army Field Artillery. One of his classmates at FA BOLC was a MMA grad and chose Army FA. I believe this can only be done if you graduated one of the academies but not sure.