Sergio Romo's storied career in the MLB has come to a close. The longtime relief pitcher threw his final game on Monday against the Oakland Athletics. It was an emotional night, as Romo has been in the league for 15 seasons.Going out with a bang, Romo decided to wear a special hat on the mound. Throughout spring training, when a kid would ask for his autograph, he would make them sign his hat in return. He received many autographs and wore that hat to thank everyone who supported him.Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:442884723Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrRomo mentioned that he decided to wear the hat in his final game because "it would be nice to not go in there alone," he told ESPN afterward.MLB fans took to Twitter to express how awesome they thought the gesture was. While autographs are a huge part of the sport, fans don't often hear of athletes swapping autographs with young fans."Little things for little people can make a huge impact. I love this. I remember watching 9 innings at the Metrodome as a kid and then waiting outside the player's exit. Gary Gaetti stopped [and] signed my baseball card and talked to me about the game for a few minutes," one fan tweeted.Matt Pomeroy@MattPomPom@PavlovicNBCS Little things for little people can make a huge impact.I love this. I remember watching 9 innings at the Metrodome as a kid and then waiting outside the player's exit. Gary Gaetti stopped signed my baseball card and talked to me about the game for a few minutes.37@PavlovicNBCS Little things for little people can make a huge impact.I love this. I remember watching 9 innings at the Metrodome as a kid and then waiting outside the player's exit. Gary Gaetti stopped signed my baseball card and talked to me about the game for a few minutes."Love this, on so many levels," another fan tweeted.Aditi Kinkhabwala@AKinkhabwalaLove this, on so many levels. twitter.com/pavlovicnbcs/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:1949Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrLove this, on so many levels. 💙💙💙 twitter.com/pavlovicnbcs/s…DC4LCustomTees.com@DC4LCustomTeesThis. Is. AWESOME!!! twitter.com/pavlovicnbcs/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:93Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrThis. Is. AWESOME!!! twitter.com/pavlovicnbcs/s…Beauty of A Game@BeautyOfAGame This is the coolest thing I've seen in awhile. twitter.com/PavlovicNBCS/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:192Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyr❤️❤️❤️ This is the coolest thing I've seen in awhile. twitter.com/PavlovicNBCS/s…Baseball fans can't get over how awesome this is. It's unfortunate that Sergio Romo is retiring because he made a ton of new fans on Monday.Grant Summers@gsummers19Sports :) twitter.com/pavlovicnbcs/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:21Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrSports :) twitter.com/pavlovicnbcs/s…Ashley Brewer@ESPNAshleyThis belongs in Cooperstown 🥲 twitter.com/pavlovicnbcs/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:482Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrThis belongs in Cooperstown 🥲 twitter.com/pavlovicnbcs/s…Keith Allen@CNNKeithOK, this made my day. twitter.com/PavlovicNBCS/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:450314790Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrOK, this made my day. twitter.com/PavlovicNBCS/s…Wendi Hansen@WendiLooHoo3What a beautiful way to remember this game, this moment. 🥹 twitter.com/pavlovicnbcs/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:54792Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrWhat a beautiful way to remember this game, this moment. 🥹❤️ twitter.com/pavlovicnbcs/s…Robbie Mack@ctcultureblogBaseball is beautiful twitter.com/pavlovicnbcs/s…Alex Pavlovic@PavlovicNBCSEvery time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight:450714795Every time a kid asked Sergio Romo for an autograph in spring training he asked them to sign his hat first. He wore this to the mound tonight: https://t.co/O3CXB5BLyrBaseball is beautiful twitter.com/pavlovicnbcs/s…This is what makes sports so great. The young fans who signed the hat will remember this moment for the rest of their lives.Sergio Romo had a storied career in the leagueWashington Nationals v San Francisco GiantsIn his 15 years in the league, Sergio Romo was a part of eight teams. Most notably, he was a member of the San Francisco Giants, where he spent nine seasons. He was an All-Star in 2013 and a three-time World Series champion.He officially took over the closer role for the Giants in 2012. He had big shoes to fill as he took over for Brian Wilson. Wilson made quite the name for himself with his on-field dominance and huge beard. It wasn't an easy transition, but Romo handled it flawlessly.While in San Francisco, he appeared in 515 games, compiling a 2.58 ERA and a 0.955 WHIP. It's been quite the career for somebody who was drafted in the 28th round of the 2005 MLB Draft.