Jurgen Klopp's men were battling in the relegation zone throughout the first half of the season but Saturday's 3-0 win over Schalke marked their fourth straight victory in the Bundesliga.
Aubameyang's goal, which made it 1-0 in the 78th minute, led to Batman and Robin masks being produced as the Gabon international and Reus celebrated.
"We always try to have a bit of fun - there wasn't a lot of that in the first half of the season and things like that always do you good. It was just meant as a little joke," he was quoted as saying by the Bundesliga website.
"We had a meal together two days ago and that's when we came up with the idea."
"Massimo, my translator, helped me. At the beginning of each half he hid the bag behind the opposition goal and that's where I got it [the cape] from," he said.
"A month ago we were talking about being in a relegation battle," he said.
"I think it's good we've pulled away from there now but we're just taking things one step at a time and we've now won four straight matches, which is very important.
"At the moment things are going well but we've got some really tough games coming up.
"If the teams above us in the table drop points, of course we'll try to catch them up, but there's a long way to go."
