Opiates (morphine and codeine) can be detected in urine for at least 48 hours after one eats food containing poppy seeds. As little as a single bagel covered with poppy seeds could produce a false positive test for these drugs.
Split-brain patients have had surgery to cut the corpus callosum. Such a phenomenon was studied and monitored by two neuroscientists Roger Sperry and Michael Gazzaniga. After hard operation, patients felt quite good although the expectations weren't that good. Patients could perform all the activities they did before surgery, that was very surprising and innovational. But after several experiments, doctors discovered side effects and got back to study this process.