Storylines
In each twelve-minute episode Ernie faces a problem, which he needs to fix with the help of the trains. This will typically involve one of the locations on International Underground or visitors coming via the Underground - often both.
| Number | Title | Writer | Synopsis |
| 1 | Pop Decoy | Louise Kramskoy | Jubilee lets slip his secret about pop superstar Sam 7. Bakerloo gets into pop. |
| 2 | Sir Clunkalot | Diane Redmond | The medieval pageant sees Ernie save a damsel in distress. |
| 3 | Mr Rails Never Fails | Diane Redmond | Ernie's heavy cold leads to confusion over the arrangements for Mr. Rails' surprise party. |
| 4 | Brooklyn and Rocky Two Shoes | Diane Redmond | American athlete Rocky Two Shoes rides over on Brooklyn and overcomes his fears. |
| 5 | Pulling Together | Jan Page | Hammersmith and City have split loyalties while Victoria gets into football. |
| 6 | Caught Purple Handed | Diane Redmond | A rather absent-minded explorer brings a rare plant to the Underground. |
| 7 | Ernie's Big Trip | Jan Page | Paris visits. Is Ernie going to France forever? Don't go, Ernie! |
| 8 | Finders Keepers | Jan Page | A Golden Ticket becomes lost property. |
| 9 | The Magician's Assistant | Diane Redmond | Millie assists as Paris brings Maestro the magician to town. |
| 10 | Cover Story | Ross Hastings | Ernie tries to take some pictures for Tunnel Times; Sydney is in town. |
| 11 | Millie's Day Dream | Ross Hastings | Millie's won a dream day. Can the Underground cope without her? |
| 12 | Mr Movie Jones | Diane Redmond | A case of mistaken identity as Mr. Movie Jones visits Sea Shell Bay. |
| 13 | Summer Breeze | Louise Kramskoy | Phew, what a scorcher on the Underground! |
| 14 | Running Late | Lisa Akhurst | Is Victoria headed for the scrapyard? |
| 15 | Light at the End of the Tunnel | Jan Page | A tiny crack opens and Miss Relic sees her mummy again. |
| 16 | The Wreck of Sea Shell Bay | Diane Redmond | Sam and Dan are seriously bad kids - but they get lucky. |
| 17 | Catnapped | Louise Kramskoy | Pippa's cat Patch goes missing as the rain pours down. |
| 18 | Monster Mystery | Jan Page | Monster on the Underground? Not a good time for a practical joke. |
| 19 | Bon Appetit | Jan Page | Millie cooks for French chef Marcel Le Magnifique, who arrives on Paris. |
| 20 | A Change Is as Good as a Rest | Diane Redmond | The trains decide to swap lines; Pippa doesn't hear the announcement. |
| 21 | Elementary, My Dear Bakerloo! | Jan Page | A jumble sale saves the nature reserve. |
| 22 | The Magic Lamp | Louise Kramskoy | Is this a genie I see before me? A theatre prop spreads confusion. |
| 23 | How Great The Art | Ross Hastings | Modern art - who wants it? How about a squashed wheelbarrow for Brooklyn? |
| 24 | The Mayor's Visit | Ross Hastings | Mr. Rails gets the wrong end of the stick. The mayor gets stuck. |
| 25 | Techno Trouble! | Lisa Akhurst | Osaka gives Jubilee some Japanese technology that is just too good. |
| 26 | Snow Go | Jan Page | The Underground suffers from the wrong kind of snow as Moscow visits. |
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