The Pokémon Company has uploaded Pokémon: The First Movie in its entirety to its official video steaming service, meaning you can watch it completely free, legally, right now (although if you're at work we'd advise against that).
Pokémon TV is available online through a web browser or via an iOS and Android app available for smart devices. While there has been no official word on why the film has been made available for free, it's likely due to the upcoming 20th anniversary of the Pokémon series on 27 February.
Pokémon: The First Movie was first released in 1998 (with a US release in 1999 and UK release in 2000) at the height of Pokémania. If you're in your mid to late 20s like me, you'll probably remember all the fuss (not to mention the free Mew trading card they gave out to young cinemagoers).
On 27 February, which marks 20 years since the release of Pokémon Red and Green (Blue in the West) in Japan, the original games as well as Pokémon Yellow will be released digitally for Nintendo's handheld 3DS system.
Shortly before this Pokémon Super Mystery Dungeon will be released for 3DS on 19 February, and afterwards sees the worldwide release of fighting game Pokken Tournament on Wii U on 18 March.