Das hört sich gut an (das Fest; nicht, dass du hier alleine feiern musst)
Here, "alleine" is used as an adverb, where I would have used "allein". I conducted a scientific investigation to gauge the popularity of the alternatives.
phrase google hits
-----------------------------
allein feiern 15 900
alleine feiern 88 600
allein gehen 139 000
alleine gehen 322 000
schnell gehen 4 340 000
schnelle gehen 17 600
"Alleine" as an adverb is more popular, but that pattern does not extend to other adjectives.
What is the difference between the adverbs "allein" and "alleine"? Are there more adjectives that follow this pattern?