Never a shortage of ideas going on back in the day ... sources NMNA archives, Fold3 U.S. Air Force photos. SDASM archives.
Part 1

Grumman F4F Wldcats with experimental wing extensions. Obviously never came to a practical use for the type. Almost looks to be a photoshop illusion.

Experimental XTDL-1 fighter aircraft that is one of two delivered for use as target drones. Bell Aerospace in Buffalo, NY c 1946, I don't see much of a difference to the P-39 here. During World War II, the U.S. Navy acquired a single P-39Q from the USAAF and converted it to a radio-controlled target drone with the designation XTDL-1. In 1946, the Navy operated two additional P-39Q drone conversions as the F2L-1K. The latter were possibly also designated as XTDL-1 orginally.

XTDL-1 fighter aircraft that is one of two delivered for use as target drones. Bell Aerospace in Buffalo, NY.

A-25A, the Army Air Forces version of the SB2C Helldiver, pictured in a hangar, possibly at Wright Field in Dayton, OH 1944. Interesting location for guns in the wings and the half white wall tires for some reason. Any ideas?

F6F-3K Hellcat of the Joint Task Force of Operation Crossroads lauched off the flight deck of USS Shangri-La (CV-38). Weird to see no pilot.

F6F-3K Hellcat of Operation Crossroads in flight preparing for testing. The base was probably at NAS Atlantic City, NJ c 1946

Navy Grumman F4F-3 Wildcat using Jet Assist to take off c 1943

P-40K 42-9870 25th FS 51st FG with belly tank configured to carry mail c 1944

P-40K 42-9870 25th FS 51st FG with belly tank configured to carry mail c 1944

P-40K 42-9870 25th FS 51st FG with belly tank configured to carry mail c 1944

P-40K 42-9870 25th FS 51st FG with belly tank configured to carry mail c 1944

F-5B of the 28th PRS with modified drop tanks for high speed Medevac ops c 1944

F-5B of the 28th PRS with modified drop tanks for high speed Medevac ops c 1944
Axis & Allied paintworks
With the island hopping campaign in the Pacific, it became apparent that a faster way was needed too get wounded from the front line.
P-38's/F-5's were used with specially designed drop tanks, that could accommodate injured servicemen.
This was a very uncomfortable way to fly. Some of the pods weren't even fitted with a window to let the victim see out or bring in light. One fellow who hitched a lift on a P-38 in one of these pods later said that whoever designed the darn thing should have been forced to ride in it!!!
F-5B of the 28th PRS with modified drop tanks for high speed Medevac ops c 1944

F-5B of the 28th PRS with modified drop tanks for high speed Medevac ops c 1944

F-5B of the 28th PRS with modified drop tanks for high speed Medevac ops c 1944

SNJ-5C Texan contracted for use by All Amercian Airways conducts testing of operating the aircraft on hydroskis in the Chesapeake Bay c 1951

FM-1 of NOTS (Naval Ordnance Testing Station) of China Lake, at Inyorkern, CA c 1943, looks to be rocket launchers

Target release mechanism on an FM-2 of VC-94 at NAS Pasco, WA 1944

P-47 with fins attached to wing tanks. P-47 42-28102 Republic P-47D-23-RA Thunderbolt (508th FG, 468th FS) crashlanded at Mokuleia AAF

P-47 with fins attached to wing tanks. P-47 42-28102 Republic P-47D-23-RA Thunderbolt (508th FG, 468th FS) crashlanded at Mokuleia AAF

P-47 with fins attached to wing tanks. P-47 42-28102 Republic P-47D-23-RA Thunderbolt (508th FG, 468th FS) crashlanded at Mokuleia AAF

AT6 with a 165 gallon wing tank equiped with heavy fins

Axis & Allied paintworks.
TODAY'S EXPERIMENTS with visual stealth have their roots in a 1943 U.S. Navy project code-named Yehudi. The intent of the program, which was highly secret at the time and came to light only in the1980s, was to give Navy patrol aircraft a better chance of sinking enemy submarines. During 1942, German U-boats took a heavy toll on merchant marine shipping off the East Coast of the United States. Aircraft scrambled to attack the U-boats, but submarine captains called for crash dives whenever they spotted approaching planes. By the time an aircraft got close enough to fire upon a sub, it had disappeared beneath the surface of the ocean.
Yehudi's inventors needed a way to make the antisubmarine aircraft harder to see, and they realized that camouflage paint wouldn't do the job: Regardless of its color, the airplane would stand out as a black dot against the sky. The only way to make the plane less visible was to light it up like a Christmas tree.
The engineers fitted a portly TBM-3D Avenger torpedo-bomber with 10 sealed-beam lights installed along the wing's leading edges and the rim of the engine cowling. When the intensity of the lights was adjusted to match the sky, the Avenger blended into the background. Tests proved that the Yehudi system lowered the visual acquisition range from 12 miles to two miles, allowing the Avenger to get within striking distance of its targets before they submerged. A B-24 Liberator bomber was also modified, with similar results.
Yehudi was not put into production, because better radar had already enabled Navy airplanes to regain the tactical advantage, but the idea was revived after air battles over Vietnam. Concerned that the big F-4 Phantom could be seen at a greater range than its much smaller Russian adversary, the MiG-21, the Pentagon started a program called Compass Ghost. An F-4 was modified with a blue-and-white color scheme and nine high-intensity lamps on the wings and body. reducing the detection range by as much as 30 percent.
F9F-3 BuNo122562 with optional angle firing gun experiment. Can't imagine this idea work too well.

F9F-3 BuNo122562 with optional angle firing gun experiment.
Would you like to see more? ....