Why can Stan Laurel use his thumb as a lighter in Way Out West?

Question

Why can Stan Laurel use his thumb as a lighter in Way Out West?

I know it's slapstick comedy but it just seems a bit random.

Answer 1

TV Tropes - Finger Snap Lighter:

One fun way of Playing with Fire is to coolly light your cigarette, cigar or pipe with a finger snap in an extravagant show of Mundane Utility.

[...]

Done by Laurel and Hardy in Way Out West (1937; probably the Trope Maker).

• Stan ignites his thumb as if it were a cigarette lighter several times; each time, Ollie stares in disbelief and tries to copy him. And eventually it works for Ollie, who reacts with horrified alarm.

[Watch Clip on YouTube]