Rat Defense, English Rat

The Rat Defense, English Rat is an irregular Queen's Pawn Game chess opening characterized by the initial moves:
The position can also arise from an English Opening 1.c4 d6 2.d4 e5. Another possible move order can be reached via the Englund Gambit: 1.d4 e5 2.c4 d6.
The English Rat has been played by top players such as Levon Aronian, Viswanathan Anand, Peter Svidler, Richárd Rapport, and Ilia Smirin.

Assessment

While 3.dxe5 dxe5 4.Qxd8, transposing into an endgame, may initially appear to be favorable for White as Black's king won't be able to castle, the pawn on c4 will restrict the mobility of the white-squared bishop, so the endgame is comfortable for Black to maintain.

Gambit lines

Lisbon Gambit: 3.dxe5 Nc6, which usually continues 4.exd6 Bxd6.
Pounds Gambit: 3.dxe5 Be6.