What are the possible uses for だって?
It can mean "but" (similar to でも):
This is often used by children, and can come across as cute or childish.
It can mean "even" (again, similar to でも):
It can mean the same as だと (or more generally, と becomes って)
This use is conversational.
From Handbook of Japanese Grammar, Masahiro Tanimori:
INFORMAL PARTICLE OR CONJUNCTION (usually used by women and children) MEANING: but, because, also, even