tbh, i don't really see that as a good theme for them.
i don't have an alternative as of now, but it really doesn't feel fitting.
Seriously? Fits the fun-loving adventurous feel I get from the team perfectly... when Gaster's not around at least, because that's when things get dark and serious.
I mean, it doesn't really fit their personalities.
Frisk's a literal child, but has seen enough crap to be more mature than she should be. She's reckless, but also kind of the "older sister" that keeps the team together.
Silver and Blaze come from a ruined future; their personalities can be described from a simple line said by Silver in Sonic Forces *cough huge disappointment cough*; "I'm an optimist, but I'm also a realist." He literally went back in time to kill Sonic just so his future would restore itself.
Jet... well, he's your brash, strong-minded, reckless wise-guy that's seen enough stuff growing up in Ninjago City to have a strong resolution. No seriously, pay attention to Ninjago as a series and you'll find that t's like any other comic book city; it has the normal part, and the deeper, darker part, putting aside giant snake attacks and robot invasions.
TL;DR, they've all seen enough serious stuff to be hardened by them, as well as not be classified as "happy go-lucky bubbly adventurers" like Star or Steven.
There's actually a
mash-up between Spaceport from Forces and Hopes and Dreams, that sounds surprisingly good; as if the two songs fit together like puzzle pieces. It also relates to them, with Spaceport being your bass-like half with pretty neat lyrics, while Hopes and Dreams acts as your light-hearted half. The lyrics tie really well into each of the group's members as well.
On the other hand, if you want to go really into it, we could avoid the norm and give the group a theme that isn't from any of their series at all, like an English cover of "
Gamushara" from Black Clover (idk why i suddenly got so into this series) that I found recently. The upbeat part in the center reflects the quartet's optimism and alignments, while certain lines can pay homage to each of the group members. Fun Fact: the Japanese word "Gamushara" translates to "reckless".
Jesus, I got really into that.