Elven and Eleven. I usually end up swapping the two around when using them! The other day my mother asked me what time it was and I told her it was elven o' clock, needless to say there was silence followed by an odd look afterwards.
And as it has already been stated, I too confuse Legos for Legolas, Greenleaf I think of Legolas and then theres the mix up with the periodic table. Chemistry was so much fun my junior year! hehe...
I also had the hardest of time reading Harry Potter and seeing the name Aragog, I immediately thought of Aragorn.
Not a hallucination, but my dog's name is Arwen
the word borrow-barrow.
Wight, white.
The name Elroy gets mistaken for Elros quite often, too.
My grandfather's name is Luther, so when I see it written I see Luthien instead.
And for some odd reason when I see a milky way bar I think of Melkor...
The word lemon becomes lembas.
When I first heard of the movie, Ella Enchanted, the only thing I heard was Ella and Immediately thought of Elladan.
For the longest of time I thought Walker Texas Ranger was of the Dunedain
And of course, I think Dunedain when I hear talk of the New York Rangers or the Rangers division in the Army.