Learn German: Es jongliert ein Clown mit Tellern. - A clown is juggling with plates.

Here, Es acts as a dummy subject to fill the first position in the sentence. This allows the real subject, ein Clown, to move after the verb. German often does this to introduce new information, set a scene, or create a bit of suspense before revealing who is doing the action.

If Es is a dummy subject, does the verb jongliert agree with it or the clown?

The verb always agrees with the real subject, which is ein Clown. Because ein Clown is third-person singular, the verb takes the -t ending. If the real subject were plural, like zwei Clowns, the verb would be plural (jonglieren), even with Es at the start.

Can I drop the Es and just say Ein Clown jongliert mit Tellern?

Yes, absolutely! Ein Clown jongliert mit Tellern is perfectly correct and means the exact same thing. The version with Es at the beginning just sounds a bit more story-like. Note that if you move another part of the sentence to the first position, this dummy Es must disappear completely (for example, Mit Tellern jongliert ein Clown).

Why does the word for plates (Tellern) end in an -n here?