So, the important thing to note here is that "as" has multiple roles. One of these roles is to compare clauses. In this role, we often have the word "as" split against the word "like," which means "similar to."
The word "as" has other uses, however. One of these is to signify "while / at the same time as." For example: "As I was mowing the lawn, a Frisbee sailed into the yard." Here the word "as" just means "while." You can check out a list of other uses of "as" here:
http://en.wiktionary.org/wiki/as#AdverbAs for the clown sentences, in the second the word "as" means "in the role of," which in this case means "dressed as," etc.