It is a fragment.
Although it has a subject and predicate, it is a subordinate clause as it starts with 'especially', indicating an adjective or adverb clause.
Answer:
a fragment
Explanation:
In the same way that my answer above is a fragment, the given sentence is a dependent clause, and as such, it cannot stand on its own; something must either be added to it or deleted from it.
fragment: a fragment
complete sentences:
It's a fragment.
A fragment is a only a piece of a complete sentence.
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fragment: Especially when Jesus Foster almost dropped the birthday cake when all the candles were lit.
complete sentences:
Jesus Foster almost dropped the birthday cake when all the candles were lit.
I laughed a lot at the party, especially when Jesus Foster almost dropped the birthday cake when all the candles were lit.
