Geez.... don't yell at me Bob, but are these jokes or riddles?
Technically, you could argue they are not, but as puns, or a play on words, they could be loosely classified under the riddle umbrella.
The problem is, as you noted yourself, that the jokes here are starting to get repeat tellings, because after a while, many of the available jokes have been used. So I thought I'd mix it up a tad with a little combo pun/puzzle. Had no idea the comedy police would be banging at my front door...