Pavement bollards have been repainted as Minions from the Despicable Me films, days after a council whitewashed the original figures.
The characters re-emerged overnight in Cumberland Street, Luton.
The artwork has split opinion on social media with one person writing "it looks like kids have been at it", while another said it was "brilliant".
Luton Borough Council urged people not to engage in "illegal graffiti".
Anonymous group #Uninvitedarts said it was responsible for the work and claimed the town "does not empower local artists".
The council, which painted over the figures last week, said it wanted the group to get in touch "to see if we can work together to encourage appropriate street art expressions in the town".
The town is preparing to launch a bid to become the UK City of Culture in 2025.
#Uninvitedarts group puts artworks in areas without permission.
It told the BBC the council wants to "promote Luton as a cultural capital but they do not empower local artists to do work, and when inspiring or thought-provoking pieces appear, they get whitewashed".
Two Minions with yellow tops and feet flanking a bollard resembling The Joker have now been painted.
Graffiti has also been scrawled on the pavement, referencing a line from a Batman film: "This town deserves a better kind of artist... and we'll give it to you".
John Maher, from Luton, who spotted the white makeover, said the original Minion paintwork should have stayed, but has now said the bollards "look like a five-year-old has poured paint over them".
"It is street art, but when they start painting on the pavement they lose their case as the council can claim these people are vandals."
Meanwhile, Chris Hobbs wrote on The Luton I Remember Facebook page: "At least they have more imagination than town planners".
The Minions first appeared in August, prompting an outpouring of public support on Facebook.
The council attracted criticism after white-washing the characters, with Karen Powell posting: "Love a minion more noticeable than plain bollards... Bananas!"