The game bundle SEGA Mega Drive & Genesis Classics (https://www.igdb.com/games/sega-mega-drive-and-genesis-classics) contains a large amount of games on the webpage, but in the API only one game is returned, sonic:

'fieldsname, url, bundles; where bundles = (80185); limit 50;' https://api-v3.igdb.com/games
[
{
id: 3192,
bundles: [
4157,
7189,
20502,
20621,
22297,
46204,
80185,
86067,
96393,
99953
],
name: Sonic the Hedgehog,
url: https://www.igdb.com/games/sonic-the-hedgehog
}
]

If you pick one of the games listed on the web page as in that bundle that is missing from the API, for example Gain Ground, the web page for Gain Ground says it is available in the following bundles:

Sonic's Ultimate Genesis Collection, Sega Genesis Collection, SEGA Mega Drive & Genesis Classics, SEGA AGES Sonic The Hedgehog

But the API responds that the game appears in the following bundles:

'fields name, url, bundles.name, bundles.url; where name = "Gain Ground";' https://api-v3.igdb.com/games
[
{
id: 3129,
bundles: [
{
id: 7189,
name: Sonic\u0027s Ultimate Genesis Collection,
url: https://www.igdb.com/games/sonic-s-ultimate-genesis-collection
},
{
id: 20621,
name: Sega Genesis Collection,
url: https://www.igdb.com/games/sega-genesis-collection
},
{
id: 91043,
name: Duplicate SEGA Genesis Classics,
url: https://www.igdb.com/games/duplicate-sega-genesis-classics
},
{
id: 96393,
name: SEGA AGES Sonic The Hedgehog,
url: https://www.igdb.com/games/sega-ages-sonic-the-hedgehog
}
],
name: Gain Ground,
url: https://www.igdb.com/games/gain-ground
}
]