'Jeg er klar og jeg smiler bredt!' is literally my favorite translated line in La Den Gå though.
And speaking of Frozen, it's one of the main reasons why I started learning Norwegian.
When used in this sense, they're synonymous.
However, they both have other meanings, in which they do not overlap:
- "Lenger" can mean "longer" as in the opposite of "shorter".
- "Mer" can mean "more" as in the opposite of "less", as well as "more often".