"Miss Nellie likes..." is a classic. You come up with similar pairs: "Miss Nellie likes broccoli but hates vegetables." The answer is that she likes anything spelled with double letters.
Here are some good riddles, what: has a horn but no honk - a rhino; gets wetter as it dries - a towel; what has bark, but no bite - a tree; has a ring, but no fingers - a telophone; has 4 legs but can't walk - a table.
