Ok, I think I understand this re-arrangement. PLEASE correct me if I'm wrong. Once we pour an acid into 2-Phenylpropanal, we should naturally protonate the Oxygen on the aldehyde. This gives it a "+" Charge, which, PERHAPS, wants a methyl group to hyper conjugate with for electron density RATHER than a little old Hydrogen. Just a postulate, and I am not sure if it correct, however it seems to make sense. With a "CH3" group, the aldehyde becomes a MORE STABLE ketone in this case, as a result of the said methyl shift. Gosh, usually the mechanism tells me all I need to know!!!!!!! Thoughts?