Messerschmitt Bf.109T

Just before the war, the German Kriegsmarine (German Navy) wanted to put a carrier into service. Borrowing ideas from both Japanese and British carriers, mainly from Akagi CV, the construction of the Graf Zeppelin began, as part of the rebuilding programme of the Kriegsmarine. Therefore, a carrier air group would've been needed, with fighters (Bf.109T) dive bombers (Ju.87C) and torpedo bombers (Fi.167).
Regarding the Bf.109T ("T" stands for Träger - carrier in German), in spite of the references for a T-0 sub-variant, it seems that it didn't exist at all. Seven earlier versions (Bf.109B, Bf.109C, Bf.109D and Bf.109E) were fitted with carrier equipment like a tail-hook, catapult fitting and a larger wingspan. Both ailerons and slats were also increased, but wings weren't designed to be foldable as it wasn't considered to be needed because the Graf Zeppelin was designed around the fighter, so it fitted on the elevators perfectly. However, wings could be dettached for transport purposes, just like in any other Bf.109 variant.
After flight catapult tests, 70 of them were to be produced by Fieseler in Kassel, powered by the DB601N and armed with two 7.92mm (0.312in) MG 17s placed on the nose and two 20mm MG FF cannons placed in the wings, which were called Bf.109T-1, but after just 7 of them being built, the carrier was cancelled. The rest of the T-1, sitxy-three of them, were built as T-2s, without carrier equipment and some T-1s may have also been converted to T-2 standards. Regarding performance, it was found to be similar to the Bf.109E-4/N, however as it could take-off and land in shorter distances, all of them were assigned to the I./JG 77, based in Norway where landing-strips were oftenly short and subject to frequent strong cross-winds. At the end of 1941 the unit replaced the T-2s for Bf.109Es.
As the interest in the carrier resurfaced in 1942, the Graf Zeppelin was back in the yards for completion, but at that time, the Bf.109T was clearly outdated, so a new fighter would've been needed, so Messerschmitt responded with their upgraded Me.155 series, but, as the carrier was cancelled again, the Me.155 was repurposed as a high altittude interceptor. Design work on that fighter was transferred to Blohm & Voss and the fighter was known as the Bv.155.
From late 1941 to early 1943, the Bf.109Ts were used as trainers until April 1943, when Jagdstaffel Helgoland was formed, operating from Düne, in the island of Helgoland, until late 1943 when the unit was rebased to Lista, in southern Norway where the unit was renamed as 11./JG 11 on 30 November 1943. The Bf.109Ts remained in service until summer 1944 when the Ts were assigned to training units in Germany.

Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Bf_109_variants#Bf_109T
2. Salamander Books - The Complete Book of Fighters
3. Signal Squadron - Aircraft In action 44 - Messerschmitt Bf-109 in Action Pt.1