Lucas is the main protagonist of Mother 3. The son of Flint and Hinawa, he is characterized as more timid than his twin brother, Claus. While playable briefly during the prologue of Mother 3, he is an NPC for the first three chapters of the game, with Flint, Duster, and Salsa being the main characters of those chapters. After reappearing in the climax of Chapter 3 against the Pork Tank, he becomes the main playable character after the three-year time skip to Chapter 4, and retains this role for the remainder of the game.
While he initially leaves his hometown of Tazmily Village to locate Duster, he quickly becomes involved in a greater struggle against the Pigmask Army. He learns PSI, and his ability to use PK Love sets him into a chase against the Masked Man to pull the Seven Needles to awaken the Dark Dragon living under the Nowhere Islands. Lucas' main party of allies includes Kumatora, Duster, and his beloved pet dog Boney.
In battle, Lucas fills the same archetype as his predecessor Ness did in EarthBound, being somewhat slow, but having a strong basic attack and access to a variety of PSI techniques such as stat boosts, Lifeup, PK Flash, and the aforementioned PK Love. Whereas the previous Mother protagonists wielded baseball bats, Lucas generally wields sticks.
Lucas' appearances in the Super Smash Bros. series have helped considerably boost his public image but not to the same extent as Ness, though this can be attributed to Lucas appearing only since Brawl. Despite this fact, Lucas became more or less of a mainstream character in gaming culture rather than remaining a curious cult character who would be known only to the highly devoted Nintendo fandom.
When Masahiro Sakurai updated the original Smabura-Ken with Ness's profile on July 17th, 2001, he said that Lucas was meant to replace Ness as a playable character, but Ness was included due to time constraints, and likely due to the cancellation in 1999 of EarthBound 64, the first version of Mother 3 that had been worked on.
Both Ness and Lucas would ultimately appear as playable characters in Super Smash Bros. Brawl.
As a playable character
Main article: Lucas (SSBB)
Lucas makes his Super Smash Bros. series debut, and by extension his international debut, in Brawl. His special moves are similar to Ness, but with some key differences. For example, Lucas' PK Thunder goes through opponents and can deal multiple hits, whereas Ness' version disappears on contact. Lucas' Final Smash is PK Starstorm, which he shares with Ness. Lucas also has near-identical physics to Ness. However, the majority of Lucas' moves completely differ from Ness, thus rendering him as a pseudo-clone of his fellow EarthBound series representative.
Lucas is currently ranked 30th out of 38 on the tier list, placing him in the E tier. His lower mid-tier placing is primarily due to the additional 10 frames he gets when grab released (a trait he shares with Ness), which makes him vulnerable to grab release follow-ups from every character, including zero-death chain grabs from Marth and Donkey Kong.
As a playable character
Main article: Lucas (SSB4)
Although Lucas was not present in the final roster upon Super Smash Bros. 4's initial worldwide release, he was later released as a DLC character on June 14th, 2015. Prior to this, his non-fighter trophy appeared in both versions of the game, while his special moves became available as custom variations for Ness' respective specials.
Lucas is currently ranked 28th out of 55 on the tier list, placing him in the C tier. In addition to tying him with Ness, this placing renders him as a high-tier character. Like Ness, Lucas no longer possesses the 10 extra grab release frames, a main contributor to his lower mid-tier position in Brawl.
Rope Snake has also become significantly more useful in two ways: the changes to hitstun canceling grant his modified down throw excellent combo potential, while his tether recovery is more reliable thanks to SSB4's new edge mechanics preventing edge-hogging. On a related note, update 1.1.3 presented a significant upgrade to Lucas' grab game, as now his tether grab has noticeably less ending lag, making it reasonably fast for a grab of its nature.
However, Lucas received various nerfs to his damage output, knockback and range, while his useful Magnet Pull and Zap Jump techniques were removed. Overall, Lucas is considerably more viable than he was in Brawl, and he has gained a dedicated playerbase and decent results in competitive play.
As a playable character
Main article: Lucas (SSBU)
Lucas returns as a playable character in Super Smash Bros. Ultimate as fighter #37. Unlike his previous appearances, he is now an unlockable character.
In his transition from SSB4, Lucas has recieved a mix of buffs and nerfs. His combo game was significantly toned down due to his down throw having more end lag and footstools being techable. He has recieved buffs, however, such as PK Freeze launching opponents horizontally making it a lethal edge-guarding technique, furthermore Ultimate's engine indirectly buffed him as the return of directional air dodges allow Lucas to have a reliable mixup in place of PK Thunder.
In the MD/VA scene Lucas has achieved great results, however, his representation in regionals and nationals has been below-average outside of Mekos, leaving his viability up for debate.