Filled with a stress relief ball. First crochet a chain to see how many stitches you need at the widest part.

Then use http://avtanski.net/projects/crochet/ to calculate a sphere pattern.

Crochet the first half and a few rows of the second half. Squeeze the stress relief ball in and continue.

At some point near the end, crochet a single round in back loops only: This will be the point that determines how wide your ‘cap’ is going to be. Count how many rows you have left to the end.

For the cap, use this number and the sphere pattern to crochet that amount of rows. Then, stop increasing, make 1 round back loop only and continue rounds normally until the cap is ‘high’ enough.

For the fuse, crochet the first round (or two) from the sphere pattern, continue without increasing: 1 round back loop only, after that normally, until your fuse is long enough. Sew the fuse to the cap, and the cap to the bomb (using the front loops on the back loop only row. Watch out for decreases!).

Crochet an F and glue it on.