IMO toasters should have double-pole switches and all the respectable ones I've worked on did. However, I did also witness an RCD trip because of someone doing just that, so certainly not all of them do.
Y filter capacitors in appliances can give you quite a nasty belt when the earthing is compromised, either not connected at all or high-impedance, usually due to a poor connection. One of the most common complaints is "I always get a shock when I touch the dishwasher and the sink at the same time!". The first thing I do is break out the tester and do an earth continuity check (high-current resistance measurement) on the dishwasher socket.