If someone gets a heart transplant, is it true that they can develop the old heart-owner's characteristics?

No but: Certain food allergies have been transferred from donor to recipient (e.g. Peanut allergy). This is thought to be due to cells responsible for the allergic reaction (mast cells) being transplanted as passenger cells along with the transplanted organ. But on the whole, no.
No. This is an urban legend or old tale. Solid organs can transmit diseases such as viral infections or cancers, but not characteristics like hair color, voice patterns, memories, favorite tastes, etc.

Related Questions

Can there be anything in specific that someone should eat after a heart transplant to aid in the recovery?

Get prof. advice. All i can tell you in this venue is that a healthy, balanced diet is important. You should discuss this with your cardiologist because other factors need to be considered such as your own internal chemistry, blood tests, any imbalances, drugs, etc. Many people may benefit from low sodium diet but the amount of protein you should have depends on your kidney status. Read more...
Healthy diet . A healthy diet with fruits, vegetables, lean meats and low fat diary products is best for overall cardiovascular health, including post heart transplant. One caveat is to wash your fruits and vegetables thoroughly with plenty of soap and water as you are more susceptible to infections now due to your immunosuppressive medications. Read more...

Are there specific laws on who qualify for heart transplant?

Sort of. Not really laws, but a way of operating. A very careful and thorough series of tests, exams, and evaluation of your support structure is needed. Read more...
Laws, no... The international organ procurement networks provide a series of rules for each specific type of organ which govern the transplant status (rank) of the candidates. Within each institution, the transplant team determines the individual suitability of their candidates. This process is constantly reevaluated, in the hopes of getting the organs to the most affected patients. Read more...

Does the new heart mend to the old parts during heart transplant?

Somewhat. The removal includes atria and ventricles and leaves some atrial, aortic, pulmonary artery to match and sew to the new donor heart. Read more...
To a degree. Interesting question. The various body parts and organs are dependent on the blood flow or cardiac output from the heart. Depending upon the degree they were compromised with the old/damaged heart, they will be rejuvenated by the new heart. Most of the old heart is removed, so that there is little to 'mend.'. Read more...

My friend have a serious heart condition, 20% heart function, 28 years old on lots of medication waiting for heart transplant now CRAVING vinegar?

Sorry. to hear about your sick friend ...I do NOT have an explanation for craving vinegar..I hope some of my Health Tap colleagues will read this answer and have some ideas! Hope this helps Dr Z. Read more...

During a heart transplant, after you take out an old heart and put a new one in, what happens if you cannot get it to beat for whatever reason? Death?

New Heart. During a heart transplant, the patient is put on a bypass machine. What this means is that the patient's blood is pumped through an external device, and then back into the patient. Kind of like an external heart. The patient is taken off the bypass machine with a new heart that beats, generally speaking. Read more...

If a 9 month old baby is having a heart transplant, can they get a 13 year olds heart?

No, too large. Heart transplants require removal of the patient's diseased heart and replacement with a healthy heart within the same space in the chest in almost all cases (called orthotopic). This space is limited by the lungs, ribs, spine and sternum which means there is not alot of range in size. Judgment about the size matching is a major aspect of heart transplantation. Best of luck. Read more...