Pinch the barb down on the size 8 hopper hook, start the fluorescent green thread and take it back to above the barb.
Prep the Green 2mm Craft Foam: cut a piece one hook length long and two hook gaps wide, mark three equal points along it and cut it to a home-plate shape. That single piece becomes both the over body and the head.
Cut one Chartreuse mop "tentacle" off the mop head. Put a dab of Zap-A-Gap on the shank where it will sit so it cannot spin, give it a couple of wraps to hold it, then fold the butt back and wrap forward to a quarter of a shank length behind the eye. Coat those wraps with more glue and clean off the loose fuzz.
Fold the foam roughly in half and position it so a little of it sits back behind and below the shank. Dab glue on the underside, set it back on the hook at that quarter-shank point and take a couple of wraps, then a cross wrap over the top to divide it into a segmented upper body and a head.
Draw the eyes on the foam head with the Black permanent marker.
Spin an inch to an inch and a half of caddis-green SLF Prism dubbing onto wetted fingers and wrap it around the segment behind the head, to help hold the legs in.
Prep the Rear Legs: divide the barred round-rubber legs down to single strands, loop each one over about half an inch and knot it to make the hopper's kneed joint, set the knot with a drop of glue and trim the excess so the leg sits at a right angle. Make a matching pair.
Position a knotted leg on each side over the dubbed segment with one or two wraps, eyeballing the joints so they line up, then cross wrap back toward the head, bring the leg ends over and secure them right behind the head and trim the excess.
For the Front Legs, loop a single strand of green round rubber, tie it in loosely on each side and drag it into place so it sits in the seam between the two brown rear legs.
Cut about an inch and a half of White Polypropylene Floating Yarn and tie it on top as the wing, extending a little past the tie-in point. Set an orange 2mm Craft Foam disc over it as the Indicator, which both flattens the yarn and makes the fly easier to see on the water.
There is no whip finish on this fly: put a dab of Zap-A-Gap on top of the wraps, tighten the thread down onto it, trim the thread off and even up the legs.