Before I say anything else, allow me to extend my apologies for the black-and-white art of Sireen seen here. The only other art I had access to for Sireen had him obscured either by text or by another character. At least this version was unobstructed. Clearly there's real, unobstructed, Sireen color art out there somewhere, but I've never seen it. If anyone's able to point me in the direction of better packaging art, I'd be grateful.
Both Fixit (on the left) and Sireen (on the right) are Micromasters. Fixit is a member of the Autobot Rescue Patrol (someday I may feature that whole team, but for now, here's the TFWiki entry), while Sireen (not to be confused with the Headmaster Siren) is a member of the Japanese-exclusive "Turbo Team" that makes up the Micromaster combiner Sixturbo. Sireen is noticeably larger than Fixit, and I can only assume that the somewhat-larger scale was put in place when Takara started doing the Micromaster Six-teams. While my Fixit is an original G1 toy (and has never been reissued), my Sireen is the reissue version from 2002, which loses the stickers of the 1992 original version, but replaces most of those features with tampographs. In general, I prefer the cleaner look of the tampographs, but in this instance, it needs to be recognized that some details (the word "Ambulance" down the side of the vehicle mode, for example) were lost in the translation.
Here are Fixit and Sireen in robot mode. Neither robot quite uses the usual "flip the feet, flip the top" Micromaster transformation, although neither is at all difficult to figure out without instructions. Sireen, however, does have the extra step of pulling out the "medical tools" (at least that's what his 2002 bio calls them) above his head, which may not be obvious unless you're looking at a fully-transformed picture.
In theory, Sireen has a third mode, being a component of a combined robot, but it's really just taking the ambulance mode as-is and sticking it on the Sixturbo combiner parts, so it's really not worth featuring.
Fixit and the Rescue Patrol can be found fairly inexpensively on eBay, while Sireen and the Turbo Team tend to go for a fair bit more. That said, Sireen's mold was also released in the US in 2004 as part of the Universe line, branded as the Protectobot First Aid, which might provide a less expensive alternative, but be aware that Micromaster First Aid has different thighs than Sireen. Either way, eBay is a far better option in these "stay at home" days than trying to find a used toys shop (which probably isn't even open right now, anyway), so if these toys interest you, why not give it a look?