A funny example of irony is a woman who falls asleep reading a book about overcoming sleep problems. Other examples include a spelling exam that misspells its instructions, or a sign advertising a construction service that falls apart.
Funny examples of irony occur when things happen in ways contrary or opposite to what one expects. People presume an English teacher, for example, is fluent in the English language and has no problem with proper spelling or grammar. It's quite ironic, then, if that English teacher makes a poster for his classroom that reads "Are kids are the future." Similarly ironic is a dentist who offers his patients candy and coffee after cleaning their teeth, or a nonstick pan whose sticker label is stuck to its surface. In all these cases, the humor comes from situations and outcomes that defy or oppose the expected result.
Irony is commonly used as a literary technique or rhetorical device, and it comes in many different forms. Situational irony is when the outcome of an event differs radically from initial expectation. Cosmic irony deals with notions of misfortune related to chance or fate, as in an eye doctor who loses his vision. Dramatic irony is used in literature, theater and film to give audiences knowledge characters don't yet have. Irony can be funny, tragic, shocking or absurd.