Spike From 'Little Giants' -- DANCING PHENOM ... The Annexation of Studio City

Spike from "Little Giants" is no longer a tackling machine ... he's a DANCING MACHINE ... and TMZ has footage showing the guy poppin' and lockin' like a friggin' CHAMP!!

19 years after he tried (and failed) to obliterate Becky "The Icebox" O'Shea ... Sam Horrigan took over the dance floor at La Maison lounge in Studio City, CA ... and totally stole the show.

We're told it all went down at an event for Ken Due clothing -- when Sam, who's a manager at the lounge, started feeling the music and decided to bust out a few moves.

The leg strength is particularly impressive ... must've been the nightly "evaporated milk" massages.