Bankia in Spain is offering a Spiderman towel to young investors as part of a drive to hold onto deposits after it was taken over by the state in a rescue costing 23.5 billion euro.
The bank is offering the prize to youngsters if they manage to save 300 euros by the end of the month. For every 50 euros saved, account holders can enter a draw for a trip to New York.
Competitors such as online bank ING Direct have aggressive advertising campaigns to poach accounts from Bankia after a report of a deposit run in early May, Reuters reports.
New chief executive Jose Ignacio Goirigolzarri said on Saturday the situation had normalised since then and he expected deposits to be higher in June than they were at the end of last year.
Bankia is Spain's fourth largest bank. It holds around 10% of Spanish deposits.