Titles of the references on the Hawaiian earring Wikipedia page, clearly designed to make math actually seem fun:

“The big fundamental group, big Hawaiian earrings, and the big free groups”

“Anomalous behavior of the Hawaiian earring group”

“The fundamental groups of one-dimensional wild spaces and the Hawaiian earring”

“The singular homology of the Hawaiian earring”

“The topological Hawaiian earring group does not embed in the inverse limit of free groups”